Burundi admitted Saturday that it had asked for an exiled Burundian opposition leader to be arrested in Tanzania and extradited to face murder charges.

"The arrest by Tanzanian police of Alexis Sinduhije was in response to an international arrest warrant emitted by the (Burundian) public ministry via Interpol" last September, the prosecutor's spokesman told AFP.

A Burundi government spokesman denied a week ago that Bujumbura had sought Sinduhije's arrest.

Sinduhije, who fled Burundi to France following disputed 2010 elections and their violent aftermath, is accused of involvement in two murders, that of Kassi Manlan, the head of the World Health Organisation's Burundi office, and his servant Nzisabira, the spokesman said.

Sinduhije's deputy has been held since last July in the same case.

The spokesman, Elie Ntungwanayo, said Sinduhije also faced charges of arms trafficking and forming armed groups.

He said the charges stem from a report by an expert UN mission to the neighbouring Democratic Republic of Congo that described Sinduhije as the leader of a new Burundian rebellion operating from the east of the DR Congo.

Observers say the arrest is part of a bid to silence the opposition in the central African country.

The head of the opposition Movement for Solidarity and Development, a former journalist, was arrested in Tanzania's economic capital Dar es Salaam on January 11 upon his arrival there from Uganda, according to his Tanzanian lawyer Habas Nyange.

Rising violence in Burundi has sparked fears of a resumption of the civil conflict that claimed some 300,000 lives between 1993 and 2006.

More than 300 opposition members were victims of extra-judicial killings last year, according to a Burundian NGO. The UN Security Council said 53 people were executed in Burundi between January and November 2011.