Police fired teargas and then live bullets in the air as a warning, and then aimed at the crowd

Eyewitness to Zanzibar clashes

Eyewitnesses spoke of running battles in the streets, with police firing repeatedly at supporters of the Civic United Front (CUF), who are demanding a re-run of last year's election.

In one incident, on Pemba, a policeman was decapitated with a machete.

The CUF has made repeated calls for a re-run of last October's poll on the islands, which international observers said was not free and fair.

Police killed at least two CUF supporters on Friday after raiding the party's offices in Zanzibar town.

Live bullets

Saturday's violence appears to have started when the police tried to prevent the demonstrations from taking place.

President Mkapa: Government banned demonstration

"The police tried to disperse some groups and people reacted," said Issa Yusuf, an eyewitness at the scene of one incident in Zanzibar Town.

He said the demonstrators threw stones and petrol bombs.

"Police fired teargas and then live bullets in the air as a warning and then aimed at the crowd. About five people fell down, but I have seen two dead."

Many of the demonstrators were reported to be carrying machetes.

Last week, the government of President Benjamin Mkapa - which won last year's elections - banned the CUF demonstrations and warned people not to take part.

The CUF had called for demonstrations not just in Zanzibar, but throughout the whole of Tanzania, to protest at the result of the election.

Election concerns

Polling in the election was relatively trouble-free on the mainland, but international monitors said it was not conducted freely and fairly on Zanzibar and its sister island, Pemba.

On Friday, the CUF chairman, Ibrahim Lipumba, was charged in the main city, Dar-es-Salaam, with unlawful assembly and disturbing the peace. He appeared in court along with 15 other CUF members on the same charges.

Mr Lipumba had injuries to his arms, which some observers said supported opposition allegations that he was beaten in the course of his arrest.