UN Secretary-General Antonio Guterres yesterday urged Myanmar to halt its military campaign against Rohingya Muslims, just hours after Aung San Suu Kyi failed to quell an international outcry in a much-anticipated address.

Addressing the opening of the UN General Assembly, Guterres said he "took note" of Suu Kyi's pledge to abide by the recommendations of a report by former UN chief Kofi Annan that has advocated citizenship for the Rohingya.

"But let me be clear," Guterres said. "The authorities in Myanmar must end the military operations, and allow unhindered humanitarian access."

More than 420,000 Rohingya have been forced to flee violence in Myanmar's northern Rakhine State in what the United Nations has described as "ethnic cleansing".

"We are all shocked by the dramatic escalation of sectarian tensions in Myanmar's Rakhine State," Guterres told world leaders.

In an interview earlier this week, Guterres described the address by Suu Kyi as "a last chance" to speak out and put in motion an end to the mass exodus.

Meanwhile, French President Emmanuel Macron has called for an end to Myanmar's military campaign, describing the plight of the Rohingya as ethnic cleansing, in his first address to the United Nations.

"The military operation must stop, humanitarian access must be guaranteed and the rule of law restored in the face of what we know is ethnic cleansing" in Rakhine state, Macron told the General Assembly.

In another development, Britain yesterday said it suspended its educational training courses for the Myanmar military due to the ethnic violence in Rakhine state.

London said it had "deep concern" about human rights abuses and would not be resuming the military courses unless there was an "acceptable resolution" to the ongoing Rohingya crisis.

"The action the military are taking against the Rohingya people needs to stop," British Prime Minister Theresa May told the UK's Sky News in New York.

"There will be no further defence engagement or training of the Burmese military by the Ministry of Defence until there's a resolution of this issue."

In London, a government spokesman said in a statement: "In light of the ongoing violence in Burma's Rakhine state, the growing humanitarian crisis it has caused, and our deep concern about the human rights abuses that are taking place, we have decided to suspend the educational courses provided to the Burmese military until there is an acceptable resolution to the current situation.

"We call on the Burmese armed forces to take immediate steps to stop the violence in Rakhine and ensure the protection of all civilians, to allow full access for humanitarian aid and to facilitate the civilian government's implementation of the Rakhine Advisory Commission's recommendations in full."

Britain's junior foreign minister Mark Field has said the UK armed forces provided vocational courses, focused on language training, governance, accountability, ethics, human rights and international law to the Myanmar military.

Britain did not provide combat training, Field said.

Some 150 members of parliament wrote to Foreign Secretary Boris Johnson on September 6 calling for the training programme to be suspended.

Nigeria's President Muhammadu Buhari urged also fellow leaders at the United Nations General Assembly to condemn Myanmar's "ethnic cleansing" of the Rohingya people.

Comparing the situation in Myanmar's Rakhine province to the massacres in Bosnia in 1995 and Rwanda in 1994, the leader of Africa's most populous nation declared: "The international community cannot remain silent."

Meanwhile, China said it supports efforts by the Myanmar government to protect its national security and opposes recent violent attacks in the country's Rakhine State, Chinese Foreign Minister Wang Yi told UN Secretary General António Guterres.

Wang told Guterres at a meeting at the United Nations on Monday, "China advocates Myanmar and Bangladesh resolve the problem via dialogue and consultation."

Wang said China sympathises with those who have fled to Bangladesh, and it would send humanitarian aid to Bangladesh.