* Cameron "disappointed" Algeria gave no warning of rescue
* Britons at risk, but number much lower than 30 people
* Cameron condemns "savage attack", offers support
LONDON, Jan 18 (Reuters) - British Prime Minister David Cameron said on Friday he was disappointed Algeria gave him no advance warning of an operation to rescue hostages held in a desert gas facility and warned that Britons caught up in the crisis were still at risk.
Promising to hunt down the hostage takers for their "brutal and savage attack", he said that the danger had not passed and that the Islamist militants still posed a threat in one part of the site, despite an assault by Algerian forces.
About 60 foreigners were still being held hostage or missing on Friday after Algerian forces stormed the complex to free hundreds of captives taken by militants, who threatened to attack other energy installations.
While contacts with the Algerian government had been good, Cameron said he was "disappointed not to be informed of the assault in advance and we do want to help in any way we can with technical help and assistance". He said Algeria had made no such request.
"We were not informed of this in advance," Cameron told parliament. "I was told by the Algerian prime minister while it was taking place."
The situation was unfolding on sovereign Algerian territory and the authorities there had the right to handle things as they saw fit, he said. He said he understood the decision to act had been taken because of an "imminent" threat to lives.
The number of Britons being held was now "quite significantly reduced" from the "less than 30" said to be in danger on Thursday evening, Cameron said. British media reports put the number at between ten and 20.
Describing how the crisis unfolded, Cameron said a British citizen was one of two people killed during the initial assault by Algerian forces on two buses travelling to a nearby airfield on Wednesday.
"It appears to have been a large, well co-ordinated and heavily armed assault and it is probable that it had been pre-planned," he said.
Cameron discussed the crisis with U.S. President Barack Obama on Thursday evening and has chaired several meetings of his government's emergency committee in the past 48 hours.
Cameron cancelled a long-anticipated speech on Britain's role in Europe on Friday to handle the security crisis, one of the gravest since he came to power in 2010.
A British rapid deployment team of diplomats and other specialists was travelling to Algiers, the Algerian capital, Cameron said.
Britain's Foreign Office said it had sent a plane to the town of Hassi Messaoud, eastern Algeria, 280 miles (450km) from the gas complex. There are staff on board who are trained to help people who have been through stressful situations.
"They are on standby to provide assistance. It's the closest they can get to the scene at the moment," a Foreign Office spokesman said.
Cameron on Friday met U.S. Defense Secretary Leon Panetta, who is London as part of an official visit to European capitals.
"Terrorists should be on notice that they will find no sanctuary, no refuge, not in Algeria, not in North Africa, not anywhere," Panetta said.