By Chelsea J. Carter and Masoud Popalzai
A man in an Afghan military uniform killed three U.S. troops Friday in southern Afghanistan, a day after the United States condemned a suicide bomb attack that left four Americans dead.
The man opened fire on the troops in the volatile Helmand province, said Maj. Lori Hodge, a spokeswoman for the International Assistance Security Force.
It is the latest in a series of so-called "green on blue" attacks that has seen attackers dressed in Afghan security force uniforms turn their weapons on NATO soldiers.
Hodge did not immediately provide details about the attack, one of a handful of attacks in recent weeks to target NATO troops.