LONDON — The deaths of five British soldiers gunned down by an Afghan policeman as they made tea after a patrol has shaken public support for the war in Afghanistan, intensifying debate about the human cost of the conflict and increasing calls for a pullout.

If British troops can't trust the Afghan colleagues they are supposed to be training, critics asked Thursday, how can they fight the Taliban? And where does it leave an exit strategy that depends on handing over control to Afghan forces?

The deaths dominated newspaper front pages, television news shows and radio phone-ins, even as the Ministry of Defense announced the death of another British soldier Thursday in an explosion in Helmand province.

Several newspapers used the same photo, of the bloodied flak jacket of one of the victims. "Gunned down as they had tea" said the Daily Mail. "A bloody betrayal," said The Times, while the Daily Mail asked: "What kind of war is this?"

Hundreds of people used Facebook and other sites to post tributes to the dead men, who included 18-year-old Guardsman Jimmy Major of the Grenadier Guards and Regimental Sgt. Major Darren Chant, the regiment's most senior noncommissioned officer.

"I don't think we ever should have gone there," said midwife Jane Cooke, 49, expressing an increasingly common view about Afghanistan. "There is an inner conflict going on there, and it's never going to be resolved."

Armed Forces Minister Bill Rammell insisted British troops must stay in Afghanistan until the country's own security forces are ready to take over.

"We do believe that the approach of partnering, mentoring and training has to be the right approach because it's about building Afghan capacity," he said. "We do not want our troops to be there forever and a day."

Britain is the largest contributor to NATO forces in Afghanistan after the United States, with about 9,000 troops in the country and 500 more committed by the government last month.

The mission had strong public support after the 2001 invasion, which came soon after the Sept. 11 attacks in the United States. But that backing has waned as casualties increase among the troops in volatile Helmand province, where the Taliban insurgency is growing.

The five British soldiers, who had been advising Afghan policemen, were shot and killed Tuesday at a checkpoint in Helmand where they were living. The gunman escaped. It was not clear whether he was a Taliban insurgent who had infiltrated the police, a genuine policeman recruited by militants or a rogue officer acting alone.

In London, sympathy for the troops was tempered by a sense of hopelessness about the conflict.