Chanting "Bush is an oil thief" and "evil is not a foreign policy", the demonstrators, some wearing traditional Muslim dress including the Islamic women's black bui-bui, tried to march from the city's centre to the U.S. embassy on its northern outskirts.

They were diverted to open ground by a small force of police but tore down U.S. flags erected for Bush's visit this weekend and burned them. The police did not intervene and there was no violence.

The protesters chanted "Who is a terrorist? Bush."

The demonstration, which began after Friday prayers, caused a major traffic jam across the narrow Selander bridge leading out of Dar es Salaam.

One of the march organisers, Sheikh Mussa Kundecha, told Reuters: "We will be the first to receive Bush by protesting against him and cursing his visit."

Bush is scheduled to arrive on Saturday night on the second and longest leg of a five-nation African tour. Tanzania is considered one of Africa's most stable and democratic nations and President Jakaya Kikwete is a favourite of Washington.

But Muslims are angered by the wars in Iraq and Afghanistan, by U.S. backing of an Ethiopian invasion of Somalia to help defeat Islamists -- and the subsequent rendition of Muslim suspects -- and by Tanzanian anti-terrorism laws which they say discriminates against them.

The fortified U.S. embassy was moved to its current location after the previous building was badly damaged in a 1998 bomb blast linked to al Qaeda and coordinated with a devastating attack on the American mission in neighbouring Kenya.