ALGIERS - An operation launched by the Algerian army to free hostages detained by an armed group in a gas field facility in the southernmost province of Illizi has ended, the official APS news agency reported Thursday, without providing the death toll of the hostages.

Citing a source at the Prefecture of Illizi, APS said the operation of the Special Forces of the army concluded by setting free 600 Algerian workers and four westerners, including two Scots, a Kenyan and a French, without providing the death toll of the hostages and the troops.

Meanwhile, a medical source in a local hospital near Illizi, told Xinhua that about 15 militants were killed in the operation and their dead bodies were subject to identification.

Earlier in the day, as many as 30 Algerian and foreign hostages managed to escape from their captors and were received by army helicopters, according to local media.

Algerian Minister of Communication Mohamed Said Oubelaid confirmed later Thursday the deaths and injuries among the hostages detained by the armed group in the ongoing gas field attack.

The Communication Minister said that "the operation launched by the National Army to free the hostages left many militants killed," adding that "Unfortunately, there were some deaths and injuries among the hostages."

"The purpose of this terrorist attack is to destroy the (Algerian) national economy which depends 98 percent on oil and gas exports," the minister said.

At dawn on Wednesday, an armed group attacked a gas-field in the locality of Tiguentourine in Illizi, killing two people and injuring six, according to official source. At least 41 foreigners were also kidnapped by the armed group called "Battalion of Blood".