KHARTOUM: The unidentified kidnappers of two foreign aid workers held in Darfur said on Saturday that negotiations with the Chadian government for their release have collapsed.

"We have had negotiations (this week) with Chadian authorities, but these negotiations have broken down," one of the kidnappers told AFP via satellite telephone from western Darfur, near the border with Chad.

But Ndjamena has denied it was in talks with the kidnappers.

"The Chadian government has no contact with this group," Communications Minister and government spokesman Mahamat Hissene told AFP in Ndjamena earlier this week.

French national Claire Dubois and Canadian Stephanie Jodoin have been held since April 4 when they were seized from their office in the South Darfur state capital Nyala, about 100 kilometres (65 miles) from the Chadian border.

The identity, motivation and demands of the kidnappers, who call themselves the Falcons for the Liberation of Africa, remain sketchy.

The hostage-taking was the second such act in Darfur since the International Criminal Court issued a warrant on March 4 for the arrest of Sudanese President Omar al-Beshir on charges of war crimes and crimes against humanity in Darfur.

Four workers with Doctors Without Borders (MSF), three of them foreigners, were kidnapped at gunpoint from their Darfur home on March 11. They were freed four days later.

Sudan expelled 13 aid agencies from Darfur immediately after the ICC issued its warrant.

The Falcons say they targeted the French relief group Aide Medicale Internationale, which employed the two aid workers, in protest at what they called the kidnapping of Darfuri children.

Chad jailed six workers with a French aid group, Zoe's Arc, in December 2007 after convicting them of trying to take 103 Darfur refugee children to France illegally.

Chadian Prime Minister Idriss Deby Itno pardoned the six within months of their imprisonment.

The kidnappers had hoped for a swift deal with the Chadian government.

"There are negotiations between us and the Chadian government, which is negotiating with us on behalf of the French government," the kidnapper said on Tuesday, without giving his name.

"We are now looking for a quick solution, especially considering the medical situation for the French hostage, because she is sick and has no medicine or healthy food or drink, and her situation is worsening," he added.

The Canadian hostage, Stephanie Jodoin, had told AFP by telephone last week that Dubois was suffering from a fever.

Troubled neighbours Chad and Sudan restored full diplomatic relations in November after a six month hiatus caused by mutual accusations of supporting armed rebels groups operating in and around Sudan's border region of Darfur.

The head of the Darfur-based Chadian rebels, Timan Erdimi, denied any involvement in the aid workers' kidnapping.

"We are not interested in Zoe's Arc," he told AFP, adding that his movement is focused on overthrowing the Chadian regime.