KABUL, Afghanistan (AP) — An Afghan police officer shot and killed three U.S. Marines after sharing a meal with them before dawn Friday and then fled into the desolate darkness of southern Afghanistan, the third attack on coalition forces by their Afghan counterparts in a week.

Four other international troops also died Friday, bringing to seven the number killed on the day in the violent south, where insurgents have their strongest roots. Three died in an attack, which is under investigation, and the fourth was killed in a separate attack, NATO said.