A total of 37 foreign workers died at an Algerian desert gas plant and seven are still missing after a hostage crisis coordinated by a Canadian, Algerian Prime Minister Abdelmalek Sellal said on Monday.

Sellal also said that 29 Islamists had been killed in the siege, which Algerian forces ended by storming the plant, and three had been captured alive.

Earlier an Algerian security source told Reuters that documents found on the bodies of two militants had identified them as Canadians, as special forces scoured the plant following Saturday's bloody end to the siege.

"A Canadian was among the militants. He was coordinating the attack," Sellal told a news conference, adding that the raiders had threatened to blow up the gas installation.

The Canadian's name was given only as Chedad.

In Ottawa, Canada's foreign affairs department said it was seeking information, but referred to the possible involvement of only one Canadian.

American, British, French, Japanese, Norwegian, Filipino and Romanian workers are dead or missing after the attack, for which veteran Islamist fighter Mokhtar Belmokhtar has claimed responsibility with his Multathameen Brigade -whose name means "The Masked Ones"- on behalf of al-Qaida.

In a video cited by the Mauritanian news website Sahara Media on Sunday, Belmokhtar said about 40 attackers took part in the raid, roughly matching the government's figures for fighters killed or captured.

The jihadists had planned the attack two months ago in neighboring Mali, where French forces began fighting Islamists this month,  Prime Minister Sellal added.

Militant group threatens more attacks if Mali operation continues 

The Mulathameen Brigade who was behind the mass hostage taking in Algeria threatened to carry out more attacks unless Western powers ended what it called an assault on Muslims in neighboring Mali, according to the SITE monitoring service. 

In a statement on Monday, the al-Qaida linked group also said the hostage-takers had offered negotiations on freeing the captives seized at a gas plant deep in the Sahara but the Algerian authorities used military force, SITE reported.

The statement was published by the Mauritania-based Nouakchott News Agency, according to SITE, which tracks statements by militants.

The group said it would attempt further such attacks if there was no halt to Western military involvement in northern Mali, which militant groups call Azawad and where French forces are fighting to end control by Islamist groups.

"We promise all the countries that participated in the Crusader campaign against the Azawad region that we will carry out more operations if they do not reverse their decision," the statement said.

The fighters seized the base on Wednesday, capturing a plant that produces 10 percent of Algeria's natural gas exports, and a residential barracks nearby. They demanded an end to French air strikes against Islamist fighters in Mali that had begun five days earlier.

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