Kabul, Afghanistan (CNN) -- Another attacker in an Afghan police uniform killed a member of the NATO forces Sunday in Afghanistan, the latest in a slew of so-called "green-on-blue" attacks. The incident took place in southern Afghanistan, NATO's International Security Assistance Force said. The attack brings to 40 the number of NATO troops killed in 32 such attacks this year, according to figures provided by ISAF. U.S. Secretary of Defense Leon Panetta urged Afghanistan on Saturday to take further steps to vet security force recruits. NATO: Most attacks on coalition troops driven by personal grievances In a telephone call Saturday, Panetta encouraged President Hamid Karzai to work closely with the commander of NATO forces in Afghanistan to counter such attacks, Pentagon spokesman George Little said in a written statement.
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NEW: An attacker in an Afghan police uniform killed a NATO service member Sunday, ISAF says
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3 ISAF troops were killed Sunday in an IED attack
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U.S. Secretary of Defense Leon Panetta called Afghan President Hamid Karzai on Saturday
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NATO says an airstrike has killed a senior Taliban leader
"During the operation, the @placeholder and coalition security force observed a large group of heavily armed insurgents engaging in insurgent activity," according to the release.