It's a deadly day in Afghanistan, with at least seven people dead in two different incidents.

In the first, a police officer opened fire on U.S. and Afghan forces inside a police headquarters in eastern Afghanistan on Monday, sparking a firefight that killed two U.S. troops and two other Afghan policemen. The attacker was also killed in the shootout, officials said.

The incident in Wardak province was the latest in a series of insider attacks against coalition and Afghan forces that have threatened to undermine their alliance at a time when they need to work increasingly close together in order to hand over responsibility as planned next year.

The attack also comes a day after the expiration of the Afghan president's deadline for U.S. special forces to withdraw from the province following accusations of abuse by those under their command.

Meanwhile, Afghan officials say U.S. troops have shot and killed two Afghan civilians as their truck was approaching an American convoy.

Interior Ministry spokesman Sediq Sediqi says the victims in Monday's incident were employees of a company that repairs police vehicles.

U.S. forces' spokesman Jamie Graybeal says the vehicle failed to heed instructions to stop as it came close to the convoy outside of the Afghan capital, Kabul, and the soldiers took "appropriate measures to protect themselves."

He confirms that two individuals were killed and says an assessment is under way.