KABUL, Afghanistan (AP) — U.S.-led troops and Afghan forces killed nine Afghan police officers Sunday, calling in airstrikes and fighting on the ground for four hours after both sides mistook the other for militants, Afghan officials said.

In a separate incident, NATO said it accidentally killed at least four Afghan civilians Saturday night. A NATO soldier also was killed in the east.

The two cases of accidental killings could further undercut popular support for the government and foreign forces operating here. President Hamid Karzai has pleaded with the U.S. and other nations fighting resurgent militants to avoid civilian casualties.