The rebels accuse the president's party of letting down Hutus

The four politicians, who are being held along with their driver, are members of the Front for Democracy in Burundi (Frodebu) - the main political party of the Hutu ethnic group in the central African country.

They were seized in the eastern province of Ruyigi on Saturday by Hutu militiamen of the Forces for the Defence of Democracy (FDD).

The rebels signed a ceasefire with Burundi's transitional government in December, but both sides have accused each other of violating the agreement and fighting has continued throughout the country.

'Bad propaganda'

The FDD's Secretary General, Hussein Rajabu, said the four MPs were being interrogated and would be released later.

"They are safe, but this is warning towards Frodebu to put an end to its bad propaganda against the FDD," he told Reuters news agency.

"For some time they have wanted to discredit our image internationally by saying our movement is against peace."

The kidnapping follows the killing by the same rebel group three weeks ago of a Hutu member of parliament from the main Tutsi party.

Civil war

An estimated 300,000 people have died in the nine-year conflict between the Tutsi-dominated army and armed Hutu groups.

Two years ago, Hutu and Tutsi political parties signed a power-sharing accord designed to end the war.

The three-year transitional government entered its second and final phase on 1 May when Domitien Ndayizeye, a Hutu and senior member of Frodebu, took over the presidency from Pierre Buyoya, a member of the Tutsi minority.

The FDD said the transition would not affect its position and has accused Frodebu of letting down the Hutu population by seeking to maintain the Tutsi-dominated status quo in Burundi.