About 650 hostages have been freed from militants at a gas facility in Algeria, state media report, but about 60 foreigners are still being held.

State-run APS news agency said those freed at the In Amenas installation included 573 Algerians and more than half of 132 foreign workers.

The militants remained holed up at the site and the Algerian army wanted a "peaceful end" to the crisis, APS said.