KABUL, Afghanistan (AP) — An Afghan soldier turned his weapon on a vehicle he believed was driven by NATO soldiers on a shared base in the south, slightly wounding a foreign civilian worker, officials said today. It was the latest in a string of insider attacks by Afghan forces against their international allies.

The attacks by Afghan soldiers and police against international forces are threatening to undermine a partnership that is key to the handover of security responsibility to the Afghan government and therefore to the entire program for the drawdown of international troops.

The Sunday evening attack in Helmand province came the same day an Afghan police officer shot and killed four American service members in Zabul, also in the south. That followed on a shooting Saturday in which a man wearing the uniform of a government-backed militia group killed two British soldiers in Helmand.

The soldier turned his weapon on a vehicle that was driving inside Camp Garmser, a shared base in Helmand, said NATO forces spokesman Maj. Adam Wojack. Another Afghan soldier disarmed the attacker and took him into custody. The assailant told interrogators he had thought he was targeting troops, Wojack said.