By Fumbuka Ng'wanakilala
DAR ES SALAAM (Reuters) - Tanzanian police fired teargas and warning shots on Tuesday to disperse thousands of people protesting against a weekend bomb attack on an opposition campaign rally, eyewitnesses said.
Supporters of the Chadema opposition party gathered in the northern city of Arusha to mourn the three people killed and the more than 50 people injured there in Saturday's blast, they said.
The latest violence in Tanzania threatens to taint the image of east Africa's second biggest economy ahead of a visit by U.S. President Barack Obama, expected to be early next month.
Eyewitnesses said riot police stepped in as the supporters started to assemble in the Soweto area of the city, making several arrests as they attempted to disperse the crowd.
"Police fired teargas at the crowd of Chadema supporters, plus several rounds of ammunitions of warning shots into the air," Daudi Lameck, a resident of Arusha, told Reuters by telephone.
"Police ordered people to disperse from the area and started firing teargas cannons. People were running everywhere after shots started being fired and I personally witnessed around 17 people were injured."
Police were not immediately available for comment.
Chadema officials have long complained about a government crackdown on opposition demonstrations and public rallies.
Commenting on Saturday's bomb explosion, Tanzania's Home Affairs Minister Emmanuel Nchimbi told reporters in Arusha preliminary police investigations showed it had been caused by a hand grenade lobbed into the crowd by an unknown assailant.
Chadema leader Freeman Mbowe said the explosion was politically motivated and said he believed opposition leaders were the intended target. Saturday's blast occurred near the main stage as Mbowe was addressing supporters at the rally.
In January, two people were shot dead in the same region when riot police fired at crowds of Chadema supporters after the authorities banned their rally.
The latest bomb attack threatens to exacerbate deep political tensions between the opposition and government in Arusha, a Chadema stronghold.
Tanzania, a nation of 45 million people, has enjoyed relative political stability since its independence from Britain in 1961, despite turmoil in some neighboring countries.
(Editing by James Macharia and Gareth Jones)