Photo: BP

Natural gas facility in Amenas, Algeria.

Five foreigners were still missing on Tuesday in the aftermath of the hostage crisis at Algeria's remote In Amenas gas plant. The Islamist group that staged the attack has threatened to attack France in the light of the offensive in Mali.

Algerian authorities are still searching for five foreigners missing since last week's attack, a source told the AFP news agency.

Work to restart production at the plant has begun, the source added, but it will take at least a week before it can return to normal.

The Signatories in Blood group has said that the attack was in retaliation for French intervention in northern Mali.

Algerian Prime Minister Abdelmalik Sellal dismissed this, saying the assault had been planned for nearly two months, long before France intervened in northern Mali.

Energy Minister Youcef Yousfi on Sunday said that wet gas production would be resumed "in the next two days".

Thirty-seven foreigners from eight different countries and one Algerian hostage were killed during the crisis, according to Algerian Prime Minister Abdelmalik Sellal said on Monday, adding that 29 jihadis also died.

Special forces managed to free 685 Algerian and 107 foreign hostages.

Mokhtar Belmokhtar's Signatories in Blood group, that claimed responsibility for the attack, has threatened further attacks, especially against France, a spokesperson told Paris Match magazine late Monday.

The France "of the crusaders and the Zionist Jews will pay for its attacks on Muslims in north Mali, but not alone, its vassals also," said the spokesperson, who called himself Joulaybib, told the magazine.

The Islamists' operation at the In Amenas gas plant was "90 per cent successful since we were able to reach a strategic site protected by 800 soldiers with only 40 men", he said.

The attackers received "logistical support" from inside Libya, a source in the country told AFP Tuesday.

Islamist groups in the country have access to weapons and other equipment and have become increasingly active since the French-backed insurrection that toppled Moamer Kadhafi.

Earlier Libyan Prime Minster Ali Zeidan denied claims that the kindappers had entered Algeria from his country.

Algerian website TSA cited a security source saying the kidnappers had entered Algeria from Libya in official Libyan vehicles, while others claimed the weapons the kidnappers used came from Libya.