The kidnappers of two Austrian tourists abducted in February in Tunisia have increased their demands in return for their release, public broadcaster ORF said on Monday.

Austria's foreign ministry did not comment on reports that the new demands included the release of a couple recently found guilty by Austrian courts of al-Qaeda membership.

Mohamed M and his wife were handed prison sentences for producing an internet video promoting Islamist terrorism.

Demands also included the withdrawal of the four Austrian peacekeepers currently stationed in Afghanistan and a substantial ransom payment.

The tourists, Wolfgang Ebner, 51, and Andrea Kloiber, 42, are being held by a North African terrorist group and are currently believed to be in Mali.

A deadline for their release was extended several times. - Sapa-dpa