The BBC's Andrew Bomford: Yemeni officials insist they had no choice

The Yemeni Ambassador was summoned by the director of the Foreign Office's Middle East desk in London, a FO spokesman said, to express "dissatisfaction over the government of Yemen's failure to co-operate fully with us in providing a detailed account".

The summons came after the UK Ambassador in Sana'a, Vic Henderson, had inconclusive talks with the Yemeni foreign and interior ministers.

Dr Hussein al-Amri: "There was no way to avoid it"

The meeting with Interior Minister Hussein Mohammed Arab, responsible for the troops who carried out the rescue attempt, was "very short", a Foreign Office spokesman said.

At a news conference in Sana'a, the interior minister repeated Yemeni statements that the hostage-takers did not want to negotiate.

"They threatened to kill the hostages if their demands were not met within one hour. They said they would decapitate them," he said.

He added that the troops heard gunfire and intervened swiftly to save the hostages.

"In 35 minutes the area was secured," he said.

Yemen's prime minister has also written to British counterpart Tony Blair saying all the tourists kidnapped by Yemeni tribesmen would have been killed if government troops had not intervened.

The FCO spokesperson said they were continuing to press for more time with senior Yemen ministers including the president to secure a full account as "it is essential that the families should know what happened".

Meanwhile the surviving western hostages have left their hotel in Aden on their way home, via the capital, Sana'a.

A British and an American women were too seriously injured to leave their hospital for now. However the other 10 survivors have begun their journey home, after being debriefed by Yemeni officials.

Differing stories

BBC Correspondent in Yemen Frank Gardner says a definitive version of events is unlikely to emerge from the hostages as their stories differ widely.

Survivor Brian Smith: "Abductors used us as human shields"

Some survivors have said they are in no doubt that the gun battle was started by the Yemeni army but they can see that the government may have had prior information that their kidnappers were preparing to execute them.

Others are convinced that the kidnappers fired first when they panicked on seeing Yemeni security forces closing in.

Several hostages have accused the Yemeni troops of firing indiscriminately while they were being used as human shields.

Lawrence Whitehouse describes his ordeal

One survivor, Lawrence Whitehouse, was still in shock when he described to the BBC how his wife was shot dead.

He said it was difficult to say who killed his wife and another hostage but the other two "were definitely killed by the terrorists".

The dead were identified as Ruth Williamson, Margaret Whitehouse and Peter Rowe from Britain and Andrew Thirsk from Australia.

Three kidnappers were killed during the rescue operation with a further three arrested and facing the death penalty.

According to Yemeni officials the kidnap gang were from an obscure Islamic group calling for the release of their jailed leader.