Tanzanian police Tuesday freed a Burundian opposition leader, Alexis Sinduhije, who was arrested two weeks ago in Dar es Salaam at Burundi's request, a senior Burundian security official said Tuesday.

"We have just learned that Tanzanian authorities did not want to follow up on our extradition request for Alexis Sinduhije to Burundi and preferred to expel him to Uganda this morning," the official said.

"At this hour, Sinduhije has already arrived in Uganda on a plane that left Dar es Salaam early this morning," adding that Burundi "regrets this unfriendly gesture by a neighbouring country, which is committed to helping us fight troublemakers."

Sinduhije's flight was confirmed by Tanzanian police and one of his lawyers, Bernard Maingain, reached by telephone in Brussels by AFP.

"I am happy to confirm that my client, Alexis Sinduhije, was freed early this morning, but I am not authorised to tell you where he is at the moment for security reasons," the Belgian lawyer said.

A former journalist, Sinduhije is the leader of the opposition Movement for Solidarity and Development (MSD) in Burundi, but he fled the small central African country after general elections in 2010 when violence broke out as the opposition contested the results. He lives in exile in France.

According to Maingain, one of his Tanzanian colleagues had on Monday filed a demand for the release of Sinduhije for procedural reasons, on the grounds that his client had not been notified of the motive for the arrest and he had not been presented before a judge within the statutory 48 hours.

The police freed him before the affair came to court.

According to a December 2011 report by the UN group of experts on the neighbouring Democratic Republic of Congo, Sinduhije is "a particularly active supporter of FNL (National Liberation Front) combatants and (the) armed rebellion in Burundi" who operate out of the DR Congo.

"Four mid-level FNL officers told the Group that FNL combatants in South Kivu (in eastern DR Congo) considered Sinduhije to be one of their movement's key leaders," the report added, giving details of his African and European travels in a bid to win financial and diplomatic support.

Burundi was devastated by a civil war between 1993 and 2006 that claimed almost 300,000 lives. A recent increase in incidents of violence in the country has led to fears of renewed large-scale conflict.