A freed hostage speaks after they were freed from a gas facility in Algeria where Islamist militants were holding them in Tigantourine, in this still image taken from video footage January 18, 2013. About 60 foreigners were still being held hostage or missing inside a gas plant on Friday after Algerian forces stormed the desert complex to free hundreds of captives taken by Islamist militants, who threatened to attack other energy installations.[Photo/Agencies]

AMENAS, ALGERIA - As many as 31 workers, including 19 foreign nationals, who were seized by an armed group in a gas field in southern Algeria, have been killed since the beginning of the Algerian army's rescue operation, a security source revealed Saturday.

The source told Xinhua that nine militants have also been killed, while three others were arrested alive, since the army's Special Forces launched the operation Thursday at the Tinguentourine gas field.

The rescue operation is still going on, the source noted.

The source said there are still "a few" hostages in the gas field complex, specifying that the Special Forces are advancing compartment by compartment in the facility.

While advancing, the Special Forces found dead bodies and workers hiding in the corners of the facility, the source added.

Xinhua reporters managed to advance to the gas plant, but could not go further due to tough security cordon by the National Gendarmerie.

"These are orders from President Office and as long as the operation is still not ended, we cannot let you access," the checkpoint chief said.