Authorities in Mali say clashes between Tuareg rebels and government troops near the border with Algeria have killed three soldiers since Thursday.
Officials say several troops were wounded and at least 29 captured in the rebel attacks in Mali's Kidal region - the same area where al-Qaida militants are reported to be holding two Austrian tourists.
The clashes are complicating efforts to free the two Austrians, Andrea Kloiber and Wolfgang Ebner, abducted on February 22 while vacationing in Tunisia and taken to northern Mali.
Al-Qaida's North African branch demanded a ransom and the release of Islamic militants jailed in Algeria and Tunisia in exchange for the two Austrians.
The demands posted on Islamic Web sites set a deadline of midnight Sunday, but Austrian officials said the ultimatum appeared to have been extended.
The kidnappers initially set a March 16 deadline for talks but postponed it at the last minute in an Internet statement posted last Monday. The group also warned that any attempt to free the hostages by force will lead to their immediate execution.
Photos of the two appeared in an Internet al-Qaida message posted Thursday.