LONDON (AP) – Fifteen British sailors and marines held captive for nearly two weeks in Iran arrived home Thursday, a day after the announcement of their release defused a growing confrontation between the two countries.

The crew, dressed in fresh uniforms supplied to them before their arrival, lined up beside the plane as photographers captured their arrival. They smiled and many stood with their hands behind their back before boarding two military helicopters at Heathrow Airport.

Wednesday’s announcement of their release in Tehran was a breakthrough in a crisis that had escalated over nearly two weeks, raising oil prices and fears of military conflict in the volatile region. The move to release the sailors suggested that Iran’s hard-line leadership decided it had shown its strength but did not want to push the standoff too far.

Iran did not get the main thing it sought – a public apology for entering Iranian waters. Britain, which said its crew was in Iraqi waters when seized, insists it never offered a quid pro quo, either, instead relying on quiet diplomacy.

Syria, Iran’s close ally, said it played a role in winning the release.

Prime Minister Tony Blair welcomed the sailors’ return Thursday but called for continued international pressure on Tehran following the deaths of four servicemen in an attack in southern Iraq earlier in the day.

The soldiers were killed in an ambush involving a roadside bomb and small-arms fire, the military said. It was the biggest loss of life for British forces since Nov. 12, when four were killed while on patrol on the Shatt Al-Arab waterway in Basra.

“Now it is far too early to say that the particular terrorist act that killed our forces was an acted committed by terrorists that were backed by any elements of the Iranian regime, so I make no allegation in respect of that particular incident,” Mr. Blair said.

Mr. Blair said Britain had managed to secure release of crew without any deal or negotiations.

On Wednesday, Iranian state media reported that an Iranian envoy would be allowed to meet five Iranians detained by American forces in northern Iraq. An American military spokesman in Baghdad said American authorities were considering the request, although an international Red Cross team, including one Iranian, had visited the prisoners.

Another Iranian diplomat, separately seized two months ago by uniformed gunmen in Iraq, was released and returned Tuesday to Tehran. Iran accused the Americans of abducting him, a charge America denied.

Those developments led to speculation that the release of the Britons had been connected to the events in Iraq. Both Iran and Britain denied any connection.