Madagascan authorities have imposed a curfew after a mob burned to death three people they claimed had mutilated and killed a local eight-year-old boy.

Government ministers flew to the island of Nosy Be on Friday to appeal for calm after a local man, a French national and an Italian were beaten and then burned on the tourist beach of Ambatoloaka on Thursday.

The government later imposed a curfew on the island to stop further violence. 

The attack happened after residents discovered a boy's mutilated body on a beach, and claimed the men had killed him to harvest his organs. 

Security forces said the two Europeans had been tortured into a confession. They were named locally as Sebastien Judalet and Roberto Gianfala. The local man was not identified.

'No risk to tourists'

An island resident, identified only as Lala, claimed the crowd had made sure the men were guilty before killing them.

"They spoke for a long time until the morning hours, and then the foreigners confessed they had killed the child. We have it on video,” he claimed, but provided no evidence.

On Friday, a pile of ash and body parts were the only recognisable signs of the earlier violence. 

Both Europeans held tourism visas, although the Italian's had expired. Local residents insisted there was no risk to tourists.

"We've got nothing against foreigners. You can come visit and there won't be a problem," said a man from the island's capital, Hell-Ville, who identified himself only as Jacob.

"We are targeting the culprits. It's public justice - we just kill them, and if you refuse to kill them we kill you because you're an accomplice." 

Mob justice is common on the vast island nation off the southeastern African coast, which authorities struggle to police effectively.

More than 255,000 tourists visited Madagascar last year. France has warned its citizens to avoid Nosy Be until calm had been restored. 

Source: Agencies