Two survivors of the Philippines hostage drama were British nationals, the Foreign Office said today.
The 12-hour ordeal on a bus in Manila ended with the deaths of eight Hong Kong tourists along with their Filipino hostage-taker after negotiations failed.
A spokesman for the Foreign Office said: "We can confirm that two of the released hostages are British nationals.
"We have offered consular assistance and stand ready to provide it if requested.
"We are not aware of any other British nationals involved."
No further details of the Britons were released.
The siege happened after sacked policeman Rolando Mendoza, 55, seized the busload of 21 tourists and four locals to demand his reinstatement to the force.
He was armed with an M16 rifle and a pistol.
The ordeal ended in bloodshed on live TV with police storming the bus and killing the gunman after he fired at the tourists, killing eight of them.
Chinese Foreign Minister Yang Jiechi said his government was "appalled" and telephoned his Philippines counterpart Alberto Romulo to voice concern.
"The Chinese government demands the Philippine government launch a thorough investigation into the incident and inform the Chinese side of related details as soon as possible," Mr Yang said, according to a statement posted on his ministry's website.
Philippines police defended their action but promised to review all events leading to the deaths.
"There will be an internal audit. We will look at whether what we did was right," national police spokesman Agrimero Cruz said.
"Of course what happened was far from ideal. Nevertheless, we are congratulating our personnel because, despite the lack of equipment... they risked life and limb."
According to newspaper reports, Mendoza was among five officers who had been charged with robbery, extortion and grave threats after a Manila hotel chef filed a complaint alleging they falsely accused him of using drugs to extort money. Mendoza was fired last year but claimed he was innocent.
As negotiations got under way in downtown Manila where the bus was parked, the outcome at first looked promising with Mendoza freeing nine hostages - six tourists, a Filipino photographer and his Filipino assistant.
Fifteen tourists and the Filipino driver were left on board.
But the situation went downhill, with Mendoza demanding a signed promise from the city ombudsman that his case would be reviewed.
By the time it arrived after hours of delays, he rejected it as insufficient.
The Filipino bus driver later managed to escape and reported that Mendoza had fired at the tourists.
The gunman was then shot in the head, police lobbed tear gas into the bus and commandos stormed the vehicle by smashing windows and the back door with sledgehammers.
Police managed to rescue eight passengers during the ordeal, many of them wounded and one of whom later died in hospital. Mendoza and seven passengers were lying dead, one of them slumped on the bus steps.
"I hid under a seat (when the gunman started to fire)," Wang Zhuoyao, 15, told reporters from hospital. "Then the police dispersed gas. People in the bus were struggling. I could hear that many people couldn't breathe."
Hong Kong leader Donald Tsang said he was "disappointed" at how the incident was handled. His government cancelled planned tour groups to Philippines and asked Hong Kong tourists in the country to leave.
According to sources, it is understood the British nationals are an elderly couple from Hong Kong.
The former British colony is now a special administrative region of China.