David Cameron condemns the "brutal and savage" actions of Islamist militants in Algeria, as the Algerian prime minister says 37 foreign hostages were killed in the gas plant siege.

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Abdelmalek Sellal also said 29 "terrorists" were killed and three of the militants who attacked the plant were captured alive.

In a House of Commons statement today, David Cameron said three British nationals are known to have died in the four-day siege, which finally ended on Saturday, and three more are believed to be dead. A Colombian national, resident in Britain, is also thought to have been killed.

Mr Cameron said: "We will contribute British intelligence and counter-terrorism assets to an international effort to find and dismantle the network that planned and ordered the brutal assault at In Amenas."

He promised a "strong security response", saying north Africa was becoming a "magnet for jihadists".

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The latest Briton to be confirmed dead is 59-year-old Scot Kenneth Whiteside, who lived in Johannesburg with his wife and two daughters. He was a planning manager at the In Amenas complex.

However, his brother said police only confirmed Kenneth's death following a posting on Facebook.

He said: "We were not given any official information and it was through Facebook, of all things, that we found out of Kenny's demise. It was my daughter who found it on Facebook, a message from an Algerian co-worker. The police came last night and informed us that what was on Facebook was true, that Kenny had been executed."

Scotland's Justice Secretary, Kenny MacAskill, said Scots caught up in the crisis have been through a "horrendous ordeal".

Garry Barlow.

'Cold-blooded murderers'

The first of the British victims to be officially named was 46-year-old Paul Morgan, reported to be a former Foreign Legion soldier and Gulf War veteran who was in charge of security at the In Amenas plant.

In a statement his family said: "Paul was a true gentleman, a family man, he very much loved his partner Emma, his mum, brothers and sister, of whom he was very proud."

On Monday afternoon, the Foreign Office released a statement by the family of 49-year-old Garry Barlow (pictured right), a married father of two from Liverpool who is believed to have died.

It said: "Garry was a loving, devoted family man, he loved life and lived it to the full. He was very much loved by myself, his sons, mother and sister and the rest of his family and friends and will be greatly missed."

Foreign Secretary William Hague branded the militants "cold-blooded murderers" and said reports they had "executed" seven of their hostages before the final battle could well be true.

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'Lack of information'

60-year-old Tony Grisedale from Cumbria said he hid for two days and managed to keep out of the way when Islamist militants seized control of the Amenas gas platform in Algeria last week. (See video above.)

Meanwhile, the family of one of the British survivors, Lewis McCloud, say they are "very relieved" he is now safe at home in Devon.

In a statement, Mr McCloud said: "I would like to thank my family and friends for all their support.

"I'm happy to be home, but my thoughts are with the families who have lost their loved ones."

Mr McCloud's brother Malcolm told the BBC he is frustrated with the British authorities, fuel company BP and recruitment company Orion, who he said failed to keep them informed.

"None of these fed any information, despite being told we would be the first to know", he said.

"The lack of information from all the relevant sources was very poor. We were kept up-to-date from friends who worked in the oil and gas industry and the news."