An Afghan policeman killed his commander and a district chief in southern Afghanistan, officials said Tuesday, in a new "insider attack" in the country after a recent decline.

An Afghan policeman killed his commander and a district chief in southern Afghanistan, officials said Tuesday, in a new "insider attack" in the country after a recent decline.

The shooting occurred in the Nawzad district of Helmand province on Monday, according to provincial police spokesman Farid Ahmad Obaid. The policeman killed his commander Shamsullah, who goes by only one name, and district chief Sayed Murad Agha.

Two other people were wounded in the incident, which also left the attacker dead.

"The attacker was wounded in an exchange of fire with the guards and later died in the hospital," Obaid said.

"We don't know the motive behind this attack yet," he added.

A Taliban spokesman, Zabihullah Mujahid, claimed responsibility for the attack on his official Twitter account, saying the policeman had defected to the militants.