(CNN)A U.S. Army soldier was killed Wednesday in an attack in eastern Afghanistan by an Afghan National Army gunman, a U.S. military official told CNN, shortly after an American official met with a provincial governor. A U.S. defense official didn't provide details about the attack in the city of Jalalabad. But an Afghan police chief told CNN that an Afghan National Army soldier shot at U.S. soldiers at a provincial governor's compound in Jalalabad on Wednesday. The Afghan soldier opened fire on the U.S. troops as they were leaving a meeting at the compound, said Fazal Ahmad Shirzad, police chief of Nangarhar province. An Afghan soldier was killed and another was injured in a subsequent exchange of gunfire, Shirzad said. It wasn't immediately clear whether the assailant was among them. A senior U.S. official had just held a meeting with Nangarhar's governor at the compound when gunfire erupted, a U.S. Embassy representative said. The embassy representative didn't identify the official but said that all diplomatic personnel had been accounted for after the incident. The U.S. military official didn't know yet what motivated the shooting. Other troops were injured in the attack, the U.S. defense official said, speaking on condition of anonymity. Those troops belong to the NATO-led Resolute Support mission meant to train and support Afghan troops. The defense official did not provide the nationalities of the injured Resolute Support troops. Most of the troops involved with Resolute Support are with the U.S. military. CNN national security analyst Peter Bergen said that despite Wednesday's incident, instances of "green-on-blue" attacks are declining overall for several reasons. "First, there are far fewer US soldiers in Afghanistan," Bergen said. "Second more counterintelligence resources were devoted to countering the threat and third, an attempt was made to better vet afghan army recruits." CNN's Masoud Popalzai and Jim Sciutto contributed to this report from Kabul, Afghanistan.
Gunfire erupts after senior U.S. official meets with Afghan governor in Jalalabad, U.S. Embassy says . Afghan soldier fires at U.S. troops, Afghan police official says .