A shadowy Darfur group which says it kidnapped three French aid workers in Chad and the Central African Republic threatened on Monday to kill them unless Paris agrees to direct negotiations.

"We want to negotiate directly with France, but France wants to negotiate through a third party like Chad. We reject that," spokesman Abu Mohammed Rizeigi told AFP by satellite phone.

"We're going to kill them because France is not negotiating directly with us."

Rizeigi's group has claimed responsibility for the kidnappings of a French agronomist with the International Committee of the Red Cross (ICRC) and two staff of relief agency Triangle in the Central African Republic (CAR) whose names have not been released.

NONE In an interview with AFP on Thursday, ICRC worker Laurent Maurice, who was kidnapped in a Chadian village near the Sudanese border, said that he was bearing up despite his ordeal, then in its 17th day.

"I have been deprived of my liberty for 17 days but I'm bearing up," he said by satellite telephone, adding that he had been able to contact his family through the ICRC.

"I am in Chad," he added, without elaborating, contradicting the account of a senior Chadian official who had said that the kidnappers had taken their hostage into the western Sudanese region of Darfur.

'Change policy'

In a separate phone call on Thursday, Rizeigi said his group was targetting France because it had failed to change tack when the group held two other aid workers, a Frenchwoman and a Canadian, earlier this year.

"We want France to change policy in the region," he said.

He said his group was the same one which held two staff of French relief group Aide Medicale Internationale for 25 days before releasing them on April 29.

"We kidnapped the two girls," he said. "At the time we asked France to change policy in the region but nothing was done."

In April, the kidnappers gave their name as the Falcons for the Liberation of Africa. The group's motives have remained shadowy ever since that abduction. It was unclear whether the appeal for a change of policy was genuine or cover for a ransom demand.

NONE "There have not been any clear political demands issued by the kidnappers. The motives have always appeared to be economic," said a humanitarian source, asking not to be named.

France has difficult relations with the Sudanese government as it hosts a leading Darfur rebel leader -- Abdel Wahid Nur, who heads the hardline faction of the Sudan Liberation Movement -- and has troops across the border in both Chad and the CAR.

Over the past three years, the armed groups in Darfur -- rebels and pro-government militias alike -- have splintered into two dozen separate factions, some of them with no clear political aims.

The ICRC has already said that it received a ransom demand for a second staff member, Gauthier Lefevre, who was abducted inside Sudan earlier this month.

The spate of abductions has hit relief efforts in the region. Six organisations suspended their operations in eastern Chad after Maurice's kidnapping, depriving 37,000 people of aid.