Algeria has begun a second military operation to rescue some 30 foreign hostages still captive by Al-Qaeda-affiliated group at a gas facility in the country’s southeast, Al Jazeera reports.

The second round of rescue efforts on Friday come as Algerian state media reported that more than 650 hostages had been freed as part of the army operation.

The state-run APS news agency said 573 of those freed were Algerians. Another 100 were among the 132 foreign workers captured at the In Amenas facility.

The Masked Brigade, an armed group who took hundreds hostage at the In Amenas facility, said on Friday that they would trade captives from the United States for the release of two terrorists jailed in the United States.

A spokesman for the group named the two as Aafia Siddiqui, from Pakistan, and Omar Abdel-Rahman, an Egyptian referred to as the “blind sheikh.”

The Mauritanian ANI news agency reported that sources close to Mokhtar Belmokhtar, believed to be behind Wednesday’s raid, had proposed that France and Algeria negotiate “an end to the war being waged by France in Azawad”, northern Mali.

Al Jazeera reported that the United States has sent a plane to the Algerian desert where it hopes to transport some of those freed to Europe for medical treatment.

The latest developments come a day after at least 30 hostages and 11 members of the Al-Qaeda-affiliated group were killed when Algerian forces stormed the desert gas plant to free the captives.

Eight Algerians and seven foreigners, including two British, two Japanese and a French national, were among the dead, an Algerian security source told Al Jazeera.

The military says some of the terrorists who took hundreds of hostages, remain holed up inside. The hostages include Algerians, as well as foreigners from at least nine countries – including the U.S., Britain and Japan.

The Algerian government said it was forced to launch the military operation because the fighters had threatened to blow up the gas plant.

The Masked Brigade said its fighters seized the workers on Wednesday in retaliation for Algeria letting France use its airspace to launch operations against rebels in northern Mali , but security experts said the raid appeared to have been planned well in advance.

The fighters came from Libya, according to the Algerian interior minister.