A man begs for help from the military from a bunker where he had hid on Thursday to escape a lynchmob in the Cibitoke district of Burundi's capital, Bujumbura. The man, who was suspected to be an 'Imbonerakure,' or member of the Youth League of Burundi's ruling party, was finally saved by the army. At least three people were killed in clashes in Burundi. Photo: AFP

 Protesters burned a man alive on the streets of Burundi's capital on Thursday, saying he was a member of the ruling party's youth wing that had attacked them during demonstrations against the president's third-term bid, a witness said.

Protesters have been on Bujumbura's streets for almost two weeks, often hurling stones at police who they say have fired live rounds, which police deny.

The confrontations have plunged the African nation into its worst crisis since an ethnically fuelled civil war ended in 2005.

"They put tires around his neck and then burned him," a witness told Reuters after seeing the man killed in the Nyakabiga district of Bujumbura, one of protest flashpoints.

Local media also reported the incident, while the Red Cross said a man was killed in Nyakabiga but, in line with its usual practice, did say how he died. It said a woman was killed in another area, taking Thursday's death toll to two.

Protesters said the victim of the burning was a member of the Imbonerakure youth wing of the ruling CNDD-FDD party, which they say has  attacked them. The government has regularly dismissed charges that Imbonerakure is fomenting violence.

Presidential spokesperson Gervais Abayeho condemned the Nyakabiga killing "in the strongest terms possible." "We don't want the situation to degenerate and take us back to those years when people were killed on the streets in broad daylight," he said.

Rallies, which have so far been confined to the capital, have included protesters by members of both ethnic groups. But diplomats say an escalation in violence could reopen old wounds.