Analysts say diamonds helped Mr Kabila pay for military support from Zimbabwe, in his two-year battle to regain control of great swathes of the resource-rich Democratic Republic of the Congo (DRC) from an array of rebel forces.

Rebels who took up arms in 1998 and are backed by Rwanda and Uganda, were also bankrolled by a share of a trade worth nearly $1 billion a year, they say. In all, half a dozen foreign countries have been sucked into fighting in Africa's third biggest country, drawn in part by the promise of its vast mineral resources."You wouldn't have Zimbabwe in there without the diamonds," said Mr Alex Yearsley, a campaigner at human rights group Global Witness. "That is their payment for having troops on DRC soil."

MrYearsley put the Kabila government share of the diamond trade at around $800 million, from which Zimbabwe took an undisclosed portion. Rebels benefited to the tune of $80 million to $100 million from diamond fields under their control, he said. "Kabila needed the diamonds. They were one of his only source of foreign exchange," Mr Yearsley added.

Congo's rich resources of rubber, ivory, timber, copper, gold and other rare minerals have drawn foreign armies and prospectors since the era of King Leopold of Belgium - the country's former colonial power - a century ago.

But recent efforts to crack down on gems that fill the coffers of fighters across the continent, have focused particular attention on the damaging role of "blood diamonds." The United States last week circulated proposals in the UN Security Council for an embargo on exports of all diamonds from Liberia, but there are still objections from African nations. The move followed bans on exports of rebel diamonds from neighbouring Sierra Leone and from Angola.

"Congo will be the next country in terms of looking at an embargo," Mr Yearsley said, adding that campaigners wanted to see a bar on all DRC gems since all sides were funding war efforts through selling the diamonds.

A UN panel investigating the links between diamonds and conflict in the Democratic Republic of the Congo reported, that it needed until mid-June for its survey because of the paucity of reliable information.

Decades of government neglect, mismanagement and corruption made it almost impossible to establish a precise and impartial picture. Mines and other sources of natural wealth are heavily guarded, and cloaked by an atmosphere of lawlessness, violence and fear, the panel said.

Analysts say the death of Mr Kabila could encourage rebels to press their claims for prime targets, including the southern diamond city of Mbuji-Mayi.

Mr Yearsley said it would also throw the diamond industry, in which Kabila was closely involved, into confusion.

"It's thrown the game wide open. A lot of people working in Congo have had a good relationship with Kabila to win contracts, some of them very untransparent."

(Reuters)