The al Qaeda group holding two Austrian hostages in the Sahara has extended by two weeks its deadline for the Austrian government to meet its demands, a service which monitors Islamist internet forums said yesterday.

The SITE Intelligence Group said al Qaeda in the Islamic Maghreb extended the deadline until April 6, adding that it was a final ultimatum.

Austrian diplomats have spent a week in Mali trying to secure the release of Andrea Kloiber, 43, and Wolfgang Ebner, 51, thought to be at an Islamist hideout in the Kidal region of remote northern Mali near the Algerian and Niger borders. The group has demanded freedom for 10 militants held in Algeria and Tunisia in return for releasing the pair. Algerian security sources have said captors also demanded a ransom.

If the demands were not met before the new deadline, "we will have exhausted what we could bear", SITE quoted the captors as saying in a statement issued on Islamist internet websites.

"Let Austria, Tunisia and Algeria be responsible for the lives of the kidnapped," it said.

Adding to the confusion, a prominent Austrian politician said Saif al-Islam, son of Libyan leader Muammar Gaddafi, was involved in negotiations, but the Gaddafi Foundation, which Saif al-Islam heads, denied this.

However, a Malian ministry source said the government suspected the hostages may in any case have been moved off Malian soil after fighting between government forces and Tuareg rebels who ambushed an army convoy in Kidal region on Thursday.