By ELENA BECATOROS and DEB RIECHMANN

Associated Press Writers

KABUL (AP) - The killing of five British troops by a rogue Afghan policeman underlines concerns about training and discipline within the ranks and possible insurgent infiltration of a police force that the U.S. hopes will be its ticket out of Afghanistan someday.

The attack caused anguish in Britain, where public support for the war has been waning. Britain is the largest contributor to NATO forces in Afghanistan after the United States, and its continued presence here is central to President Barack Obama's strategy as he weighs dispatching tens of thousands more U.S. troops.

The five British soldiers, who had been advising Afghan policemen, were shot and killed Tuesday at a checkpoint where they were living in the volatile southern province of Helmand. Another six soldiers were wounded, as were two Afghan policemen when the soldiers returned fire, officials said.

The gunman escaped and his motive was unclear.

The incident, which echoed two police shootings of U.S. soldiers last year, raised questions about whether international forces are trying to recruit and train Afghan police too quickly.

``There isn't a lot of vetting of police before they are hired,'' Peter Galbraith, the former top American official at the U.N. mission in Afghanistan, told BBC Radio 4.

In September, Sen. Carl Levin, D-Mich., called for increasing the size of the Afghan army and police ``much faster than presently planned'' instead of sending tens of thousands more Americans to fight here.

In Washington, Defense Department press secretary Geoff Morrell defended Afghan forces and the international training effort, a main part of the U.S. strategy for the war.

``However tragic and criminal this act was, it represents a rare and, luckily, thus far isolated incident. (NATO) troops continue to partner effectively with the Afghan national security forces and continue to build their capacity to take the lead in ultimately defending their country on their own.''

In October 2008, a policeman threw a grenade and opened fire on a U.S. foot patrol, killing one soldier. The previous month, a policeman opened fire at a police station, killing a soldier and wounding three before he was fatally shot.

Training and operating jointly with Afghan police and soldiers, as the British were doing Tuesday, are key to NATO's strategy of dealing with the spreading Taliban-led insurgency and, ultimately, allowing international forces to leave Afghanistan.

But obstacles are far greater with the police than with the army.

A Defense Department Inspector General report, released in September, found that Afghan police are crippled by serious corruption and subject citizens to frequent street-level ``shake-downs.'' Senior officials lack control of their personnel and do not routinely monitor job performance, the report said.

``Unlike the Afghan National Army, which is the most respected institution in the Afghan government, there is a wide consensus that many elements of the Afghan National Police are too corrupt, and too tied to politics and power brokers,'' former Pentagon analyst Anthony Cordesman wrote last month.

``Realistic efforts to shake out new units, give them continuity of effective leadership, deal with internal tensions and retention problems, and help them overcome the pressures of corruption and power brokers take time,'' Cordesman said.

Afghan President Hamid Karzai sought not to highlight the Afghan policeman's role in the deaths of the five British soldiers. His first statement condemning the attack said it was carried out by a member of the national police. A corrected statement, released about an hour later, didn't mention the police at all.

Downplaying the incident, Karzai's spokesman Humayun Hamidzada called it an isolated attack.

``In the U.S., people shoot up people in a shopping mall,'' Hamidzada told The Associated Press. ``There are crazy people everywhere.''

However, Karzai's main challenger in the recent election, former foreign minister Abdullah Abdullah, said the ongoing violence showed Karzai's administration has failed to stabilize the country despite eight years of assistance from international forces.

``In the absence of a credible and reliable and legitimate partner, more soldiers, more resources'' are needed to fight the war, entering its ninth year, Abdullah told reporters.

In London, Prime Minister Gordon Brown, trying to rally support for the war, warned against judging the entire Afghan police force on this one incident. The latest deaths bring the British death toll in the war to 229.

Hours before Tuesday's attack was made public, a senior Labor figure, former Foreign Office minister Kim Howells, broke with Brown and called for a phased withdrawal of British forces, arguing that the money could be better spent protecting Britain's borders.

Afterward, Howells said the shootings show how hard it will be for Britain and the U.S. to bring the Afghan army and police to the point where they can provide their own security.

``This is a real blow because it strikes right at the heart of that policy,'' he said.

Last month, Brown announced plans to send another 500 British troops to add to the 9,000 already in Afghanistan. But as fatalities rise, public support for the war has fallen. That has prompted British military officers, who normally avoid the limelight, to take the unusual step of publicly urging Brown to increase the number of troops even more.

Brown told the House of Commons that although evidence was still being gathered, ``the Taliban have claimed responsibility for this incident.'' However, his office was unable to provide details of any specific statement made by the Taliban.

Lt. Col. David Wakefield, spokesman for the British forces in Helmand, said the assailant was ``possibly acting in conjunction with one other'' when he opened fire at the checkpoint in the Nad-e-Ali district.

The Interior Ministry's head of the criminal investigation police, Jamil Jumbish, said the attacker joined the local force about 18 months ago and was from Helmand.

A Helmand police official said authorities searched through the night and on Wednesday for the attacker. He said the assailant had graduated from a regional police academy.

The official, who spoke on condition of anonymity because of the sensitivity of the case, said the motive was unclear.

Associated Press Writers Amir Shah and Heidi Vogt in Kabul, Noor Khan in Kandahar, Jennifer Quinn, David Stringer, Danica Kirka, Gregory Katz and Jill Lawless in London, and Pauline Jelinek in Washington contributed to this report.

11/04/09 21:20 © Copyright The Associated Press. All rights reserved. The information contained In this news report may not be published, broadcast or otherwise distributed without the prior written authority of The Associated Press.