An incident that began with rocket fire targeting U.S. bases in eastern Afghanistan has left at least six suspected insurgents and two civilians dead, officials said Tuesday.

According to U.S. Forces Afghanistan, insurgents fired "multiple rockets at Forward Operating Bases Rushmore and Sharana overnight. The complex attack began shortly after midnight and ended when Coalition Forces responded to disrupt the assault."

Counter-battery fire and aircraft were called in, killing six suspected insurgents. But a news release read, "Regrettably, two individuals not involved in the attack were killed and four others were injured in the battle."

"We are investigating these actions to determine what happened in Paktika," Col. Greg Julian, U.S. Forces Afghanistan spokesman, was quoted as saying. "We take the safety of Afghan civilians very seriously and sincerely regret this loss of life."

Separately, officials said U.S. troops were investigating reports that "a number" of civilians were injured when a makeshift bomb was detonated outside of Forward Operating Base Salerno.

Civilian casualties have become one of the crucial issues of the Afghan war.

U.S. airstrikes blamed last week for civilian deaths in Farah province led Afghan President Hamid Karzai to demand an end to all such strikes in the country. They were also reportedly a factor in the dismissal of the U.S. Forces Afghanistan commander, Gen. David McKiernan.

Lt. Gen. Stanley A. McChrystal has been named as his successor.