With a cannon blast and a piercing whistle, Britain and France on Friday marked 100 years since soldiers emerged from their trenches to begin one of the bloodiest battles of World War I at the River Somme.

Under grey skies, unlike the clear sunny day that saw the biggest slaughter in British military history a century ago, the commemoration kicked off at the deep Lochnagar crater, created by the blast of mines placed under German positions two minutes before the attack began at 7:30 am on July 1, 1916.

A lone piper walked around the edge of the crater at the ceremony, to be followed by a main event attended by the British royal family and Prime Minister David Cameron, as well as French President Francois Hollande and former German president Horst Koehler.

The commemoration ceremony will be held at the Thiepval Memorial, which honours more than 72,000 missing servicemen.

Just over a week after Britain's vote to leave the European Union, Hollande highlighted the friendship that saw British and French soldiers fight side by side.

"I want to recall that it is the European idea which allowed us to overcome divisions and rivalries between states, and which has brought us peace for the past 70 years," Hollande said in a statement before the ceremony.

Britain's Prince William on Thursday paid tribute to a generation lost at the Battle of the Somme at the start of an all-night vigil in memory of the Allied soldiers who would have been preparing themselves to charge the German side.

The following day some 20,000 soldiers were mowed down -- after a week of bombardment failed to destroy German defences -- in the deadliest day in British military history.

Another 30,000 were wounded and maimed.

Gravestones are illuminated ahead of a vigil at the Thiepval memorial ahead of the 100th anniversary of the Battle of the Somme in Thiepval. Photo: Reuters

"We lost the flower of a generation, and in the years to come it sometimes seemed that with them a sense of vital optimism had disappeared forever from British life," said William, attending alongside his wife Kate and brother Prince Harry.

"It was in many ways the saddest day in the long story of our nation."

The Battle of the Somme lasted 141 days, involving troops from across what was then the British Empire, and left around one million dead, injured or missing while moving the frontline only a few miles.

"Tonight we think of them... We acknowledge the failures of European governments, including our own, to prevent the catastrophe of world war," said Prince William.

London observances

The attritional battle became a defining event in the war, symbolising the horrors of trench warfare and the futility of the conflict.

"Imagine yourself, standing in a trench with water well over your knees... while thousands of unseen shells come shrieking and whining overhead. There is a very slight pause -- then it bursts and a tearing, rumbling blinding crash... hurling thousands of red-hot splinters in all directions, killing or maiming all they happen to strike," wrote Private Albert Atkins, who survived the war.

The ceremony at Thiepval is one of six in France, while Britain observed two minutes of silence to recall the moment when British, Commonwealth and French forces went "over the top" a century ago.

Then at 7:30 am sharp in Parliament Square in London, soldiers blew whistles -- the signal for the start of the offensive.

The observance came at the end of a night-long vigil in Westminster Abbey -- the first such vigil in the Abbey since the 1962 Cuban Missile Crisis -- which was attended by Queen Elizabeth II when it started on Thursday.

A century on, the eerily calm, bucolic Somme farmlands belie the slaughter wrought there, and are now the haunt of tourists visiting some 400 war cemeteries across the region, and the overgrown warrens of trenches.

About 10,000 visitors are attending the commemoration ceremony under heavy security which has the rolling fields under lockdown, with only shuttles heading back and forth to the memorial.

"It's quite emotional in a way. I feel it's important to remember these things," 73-year-old Irishman William Vernon said on Thursday as he arrived for the ceremony.

Vernon said he was coming to remember his great-uncle -- also named William -- who died aged 26 in the battle.

Vernon's son, William, 33, said his forebear died "in the most horrendous conditions. It was an absolutely awful war, a pointless war. To be in the trenches was absolute torture," he said.

Only nine out of the 39 registered political parties that contested Sunday's national election have secured parliamentary seats.

The Awami League saw its victory in 259 seats while the Jatiya Oikyafront, comprised of the BNP and other opposition parties, won in only five.

The BNP took part in the polls with its Chairperson Khaleda Zia behind bars on corruption charges.

The Jatiya Party, a component of the AL-led Grand

Alliance, secured 20 seats, the second highest number of seats won by a party.

The Workers Party of Bangladesh became victorious in three constituencies.

Dr Kamal Hossain-led Gono Forum, a key component of Jatiya Oikyafront, Bikalpa Dhara Bangladesh, and Jatiya Samajtantrik Dal got two seats each.

Besides, Bangladesh Tarikat Federation and Jatiya Party (Monju) bagged one seat each. Independent candidates won in three out of total 299 constituencies.

Voting was suspended in Brahmanbaria-2 following violence.

Election to Gainbandha-3 is due on January 27 as the Election Commission postponed the polls schedule for the seat after BNP candidate TIM Fazley Rabbi died on December 20.

Malaysia decided on Friday to carry on with a regional soccer tournament co-hosted by Myanmar, days after a Malaysian minister said it was considering pulling out in protest against Myanmar's bloody crackdown on ethnic Rohingya Muslims.

The decision came amid growing calls for Muslim-majority Malaysia to take a strong position and as protesters held simultaneous rallies on Friday in three Southeast Asian countries against Buddhist-majority Myanmar's actions in Rakhine state.

A withdrawal by Malaysia from the ASEAN Football Federation Suzuki Cup, which began on Saturday, would have run counter to the 10-member Association of Southeast Asian Nations' long-standing policy of non-interference in other members' affairs.

"The cabinet decided today that we should proceed with our match tomorrow," Malaysian Youth and Sports Minister Khairy Jamaluddin told reporters before attending Friday prayers.

Khairy said on Wednesday that he had asked the cabinet at a pervious meeting about withdrawing from the tournament, and that Malaysia "must continue to speak up" regardless of the decision on Friday.

His comments were in response to a call by a Malaysian Islamic cleric for Malaysia to pull out of the tournament, which started on Saturday and is co-hosted by the Philippines.

The conflict in Myanmar's northwestern state of Rakhine has sent hundreds of Rohingya Muslims fleeing to Bangladesh and poses a serious challenge to Nobel Peace Prize winner Aung San Suu Kyi, who swept to power last year on promises of national reconciliation.

Escalating violence has reportedly killed at least 86 people and displaced some 30,000. Myanmar soldiers have also been accused of sexually assaulting dozens of women from the persecuted minority.

The bloodshed is the most serious since hundreds were killed in communal clashes in Rakhine in 2012, exposing the lack of oversight of the military by Suu Kyi's seven-month-old administration.

Protesters in Malaysia, Indonesia and Thailand were holding rallies at the Myanmar embassies of each country on Friday seeking an end to oppression of ethnic Rohingya.

Malaysia's Youth and Sports Minister Khairy Jamaluddin speaks at a news conference in Kuala Lumpur, Malaysia November 23, 2016. File Photo: Reuters

The minister and secretary to the civil aviation and tourism ministry will attend office at Hazrat Shahjalal International Airport to implement a work plan for fulfilling international standard security at the airport by March 31.

Minister Rashed Khan Menon and Secretary Khorshed Alam Chowdhury will continue office there until March 31 to implement the plan, a civil aviation official, seeking anonymity, said.

The decision was made in an emergency meeting held at the Dhaka airport today, the official added.

Civil Aviation Chairman Air Vice-Marshal Sanaul Haque, acting managing director of Biman Bangladesh Airlines Asaduzzaman and high officials of the ministry attended the meeting with Menon in the chair.

Following recommendation from security experts and the aviation team, the minister said overall security in and around Dhaka airport is being reorganised to implement the plan, the official informed.

The United Kingdom may suspend passenger flights from Dhaka, if the overall security at Dhaka airport is not improved by the timeframe, he added.

A specialised team has been formed to modernise the airport, the official said.

The UK government has already suspended direct cargo flights from Dhaka citing inadequate security measures at Hazrat Shahjalal International Airport.