U.S. boosts intelligence after Afghan insider attacks

WASHINGTON (Reuters) - The Pentagon said on Tuesday it was expanding counterintelligence staff in Afghanistan after a rise in insider attacks by Afghans thought to be friendly to U.S. forces but who have killed 37 coalition troops so far this year.

Last Friday, six U.S. troops were killed in two separate incidents, one which saw an Afghan police commander and several of his men kill three U.S. Marines after inviting them to a Ramadan breakfast to discuss security.

Defense Secretary Leon Panetta said he was deeply concerned by the killings "because of the lives lost and because of the potential damage to our partnership efforts."

The increasing number of incidents have eroded trust between the allies just as NATO combat troops prepare to hand over security control to Afghan forces by 2014.

General Martin Dempsey, chairman of the U.S. military's Joint Chiefs of Staff, said at the same news conference that the U.S. military was bolstering counterintelligence expertise at the battalion level and above in Afghanistan.

He said the same was occurring within Afghan forces, which he said had so far discharged hundreds of soldiers who showed a risk of radicalization -- including travel back and forth to Pakistan, where many militants enjoy safe haven.

So far in 2012, there have been 29 attacks, resulting in 37 coalition deaths, 21 of which were among U.S. forces. For the same period last year, there were 16 attacks and 28 deaths.

In all of 2011, there were 35 coalition troops killed, 24 of whom were U.S. troops.

(Reporting by Phil Stewart; Editing by Eric Beech)