The death toll from the siege at a natural gas plant in the Sahara has climbed past 80 as Algerian forces searching the refinery for explosives found dozens more bodies, many so badly disfigured it was unclear whether they were hostages or rebels fighters, a security official said.

Algeria said after Saturday's assault by government forces that at least 32 rebels and 23 hostages were killed.

On Sunday, Algerian bomb squads, sent in to blow up or defuse the explosives, found 25 more bodies, said the security official, who spoke on condition of anonymity.

"These bodies are difficult to identify. They could be the bodies of foreign hostages or Algerians or terrorists,'' the official said.

In addition, a wounded Romanian who had been evacuated died, raising the overall death toll to at least 81.

Algerian special forces stormed the plant on Saturday to end the four-day siege, moving in to thwart what government officials said was a plot by the Islamic extremists to blow up the complex and kill all their captives with mines sown throughout the site.

Bodies discovered

Ennahar, a private Algerian TV station known to have good sources within Algerian security, said the 25 bodies were believed to belong to hostages executed by the captors. 

With so much still unknown about the fates of foreigners held at the sites, countries that have faced casualties have yet to issue final counts of the dead.

Christina Hellmich of Reading University discusses the role of al-Qaeda in the North African region

The gas refinery was run jointly by Britain's BP and Norway's Statoil with the Algerian state oil company.

A Japanese engineering firm and a French catering company also operated there.

Some governments have expressed frustration at not being informed in advance of the Algerian authorities' plans to storm the complex.

However, Britain and France both defended the Algerian action in public.

"It's easy to say that this or that should have been done," Laurent Fabius, French foreign minister, said.

"The Algerian authorities took a decision and the toll is very high but I am a bit bothered ... when the impression is given that the Algerians are open to question. They had to deal with terrorists."

For his part, David Cameron, UK prime minister, said in a televised statement: "Of course people will ask questions about the Algerian response to these events, but I would just say that the responsibility for these deaths lies squarely with the terrorists who launched this vicious and cowardly attack.

"We should recognise all that the Algerians have done to work with us and to help and co-ordinate with us. I'd like to thank them for that. We should also recognise that the Algerians too have seen lives lost among their soldiers."

Belmokhtar claim

The statements came as a veteran North African fighter claimed responsibility on behalf of al-Qaeda for the hostage crisis, a regional website reported on Sunday, tying the desert siege to France's intervention across the Sahara in Mali.

"We in al-Qaeda announce this blessed operation," Mokhtar Belmokhtar said in a video, according to the Sahara Media website, which quoted from the recording but did not immediately show it.

"We are ready to negotiate with the West and the Algerian government provided they stop their bombing of Mali's Muslims."

Belmokhtar, a one-eyed veteran fighter who fought in Afghanistan in 1980s and in Algeria's civil war in the 1990s, was quoted by Sahara Media as saying: "We had around 40 jihadists, most of them from Muslim countries and some even from the West."

His fighters launched their attack on the In Amenas gas plant before dawn on Wednesday, just five days after French forces began bombardment of Ansar al-Dine-led fighters to halt their advance in neighbouring northern Mali.

Algerian officials say Belmokhtar's group was behind the attack but he was not present himself.

Source: Al Jazeera and agencies