* Arrested opposition leader spearheaded protests in 2011
* President Museveni is accused of authoritarianism
* Arrest of opposition leader may damage president's image
By Elias Biryabarema
KAMPALA, Oct 4 (Reuters) - Police in Uganda on Thursday arrested Kizza Besigye, the country's most prominent opposition leader, after firing teargas to disperse his supporters at an anti-government rally in Kampala, the police said.
Besigye, who heads Uganda's biggest opposition party, Forum for Democratic Change (FDC), lost a presidential election in February last year to President Yoweri Museveni, who has been in power for over 26 years.
Besigye denounced the poll as fraudulent and has since refused to recognise the current government. His supporters were at the forefront of widespread anti-government street protests in 2011, which were harshly put down by police.
His arrest is likely to be viewed dimly by the United States which has told Museveni to consider his legacy. Initially lauded for reviving Uganda's economy and "restoring" political stability, Museveni has come in for international censure over his increasingly authoritarian rule.
In the past week, opposition activists have tried to revive the protest movement at a time when the government is spending big to stage elaborate celebrations next Tuesday to mark fifty years of independence from British colonial rule in what is East Africa's third biggest economy.
The main focus of their anger is alleged official corruption and human rights violations. Police say the demonstrators' aim is to topple Museveni by stirring up violence and chaos.
"We have (Besigye) and we're interrogating him and when we are done we will charge him with appropriate offences related to incitement and violence," Ibn Ssenkumbi, a police spokesman, told Reuters.
"These people are just after using violence to achieve their ends."
One witness told Reuters police had used live rounds to break up the demonstration and to chase away Besigye's supporters, a claim backed up by the local Daily Monitor newspaper.
However, the police said "lawful means" were used to disperse the crowd and pointed out that Besigye did not have permission to hold a protest.
"Police suddenly swooped in and attempted to arrest Besigye, which appeared to anger his people, and they immediately started to fight with police and form a protective shield around him," Susan Mutima, 35, told Reuters after witnessing the clashes.
"When police realised Besigye's supporters were determined to prevent his arrest they fired tear gas and live rounds to break up the crowd. Everyone scampered," she added.
Ingrid Turinawe, head of FDC's women's league, said Besigye had been under de facto house arrest for the three days preceding his arrest but had somehow managed to evade the police at his home in order to meet his supporters.
"Police brutality won't deter us," said Turinawe. "They have arrest over 30 of our supporters in the last few weeks on trumped up charges but we won't relent."
A statement from the Uganda Journalists Union (UJU) said police had assaulted two local journalists as they tried to cover Besigye's arrest, destroying their cameras in the process. (Writing by Drazen Jorgic; Editing by James Macharia and Andrew Osborn)