Algerian special forces have killed 11 rebels in what is described as a final assault to retake the In Amenas gas facility.
The state news agency APS says seven foreign hostages have been killed by militants.
That brings to between 19 and 37 the number of hostages killed during the four-day stand-off.
The gas complex was seized by al-Qaeda linked gunmen on Wednesday.
Although hundreds of hostages were released, several people are still unaccounted for.