Underwater explorers in Madagascar say they have found what is thought to be the treasure of notorious Scottish pirate William Kidd.

Soldiers on Sainte Marie Island have been guarding the 50kg silver bar after divers brought it to shore.

Madagascar's president as well as UK and US diplomats received the suspected treasure at a ceremony on the island.

Capt Kidd was executed in 1701 for piracy after returning from a voyage to the Indian Ocean.

'Scepticism'

The BBC's Martin Vogl tweets from the ceremony that the respected American underwater explorer Barry Clifford believes the 17th Century silver bar is from the wreckage of the pirate's ship.

Barry Clifford led a team which discovered the suspected treasure.

Soldiers watched over the silver at a ceremony attended by the president and diplomats. Photo taken from BBC

The 50kg bar was discovered off Madagascar's coast. Photo taken from BBC

Our reporter says there is much excitement in Madagascar about the discovery and Mr Clifford's team has no doubt that the discovery is genuine.

The team believes the bar has its origins in 17th Century Bolivia and that the ship was built in England.

However, there is bound to be scepticism and calls for more proof that the bar was linked to Capt Kidd, our reporter says.

One option would be to take samples of wood from the ship to check whether it came from England, he adds.

In 1984, Mr Clifford found the wreckage of the Whydah, a pirate ship which sank off the US coast in 1717.

UK ambassador to Madagascar Timothy Smart said he hoped that Mr Clifford's latest discovery would raise Madagascar's profile as a tourist destination.

Who was Captain Kidd?

He was thought to be born in Scotland's Greenock or the Dundee area in about 1645, and had been appointed by the Crown to tackle piracy and capture enemy French ships.

In 1698, he looted the Armenian ship the Quedagh Merchant, which was apparently sailing under a French pass.

There have been numerous searches for William Kidd's loot. Photo taken from BBC

He appeared before the bar of the House of Commons before his execution. Photo taken from BBC

However, the captain of the ship was an Englishman and Capt Kidd was executed in London in 1701.

The Quedagh Merchant had been carrying satins, muslins, gold and silver when she was attacked by Kidd.

It is thought that a large amount of the booty belonged to the British East India Company.

As well as the piracy charges, Capt Kidd was accused of murdering one of his crewmen during a row in 1697.

During Capt Kidd's execution, the first rope put around his neck broke, so he was strung up a second time. That rope also snapped but the third one held.

Capt Kidd's body was dipped in tar and hung by chains along the River Thames to serve as a warning to would-be pirates.

Legend had it that Capt Kidd hid much of his loot, which has prompted numerous treasure hunts around the world and inspired Robert Louis Stevenson when writing Treasure Island.