The former South African president, Nelson Mandela, has warned that the absence of two key rebel groups is a serious drawback to talks aimed at ending the six-year civil war in Burundi.

Mr Mandela is chairing the talks which start in the northern Tanzanian town of Arusha on Monday with a summit of seven African heads of state - including his successor Thabo Mbeki - and two European ministers.

A plenary session of 18 Burundian delegations is due on Tuesday. The talks are aimed at ending the conflict between the Tutsi-led army and extremist rebel groups from the Hutu majority.

Warning

Mr Mandela arrived in Arusha on Sunday, with the participation of the radical wings of two Hutu groups, the Forces for the Defence of Democracy (FDD) and the National Liberation Forces (FNL), still unconfirmed.

"If we want to bring peace in Burundi, these rebel groups have to be included. And I believe in that," Mr Mandela said.

"This process must be all-inclusive. It must include not only the 18 political parties but also armed groups on the ground," he added.

The presidents of Uganda, Tanzania, Kenya, Mozambique, Rwanda and Burundi are scheduled to participate in Monday's talks.

French Minister for Cooperation Charles Josselin, UK Foreign Office minister Peter Hain and Washington's special envoy for the Great Lakes, Howard Wolpe, were also scheduled to attend.

US President Bill Clinton will participate via video conferencing, addressing delegates on Tuesday.

Amnesties

The Arusha talks began in June 1998, bringing together 18 delegations from Burundi's government, parliament, opposition parties and some rebel groups.

The talks made little progress and did nothing to stop the bloodshed, which began in 1993 after the assassination of the country's first elected Hutu president, Melchior Ndadaye.

Hutus form 85% of Burundi's population but political power is held by the Tutsi minority.

Most Burundians are peasant farmers who have suffered enormously.

More than a million people have been displaced by the war and more than 200,000 killed since 1993.

More than 345,000 Hutus remained confined in army-run camps and restricted from tending their land during the year's main planting season.

There are many issues to be hammered out in Arusha, including the questions of amnesties and how to integrate rebels into the army.