Four Afghan policemen were killed and another seven wounded when one of their colleagues opened fire on them in the volatile southern province of Kandahar, an official said on Thursday.

The rogue policeman was shot dead by another officer in the incident late Wednesday night, said Zia Durrani, spokesman for the provincial police.

The shootings, which took place in the Zhari district, are the latest in a string of recent insider attacks in Afghanistan. Last month a rogue cop in Uruzgan province shot dead 10 colleagues.

The Taliban claimed responsibility for the Wednesday night attack.

The Taliban consider Kandahar their heartland, along with neighboring Helmand where poppy production accounts for most of the world's heroin.

Insurgents have attacked most districts across Helmand in recent months, in an effort to reclaim and protect smuggling routes for drugs, minerals, arms and men.

The U.S. military announced that it would boost its presence in Helmand, where Afghan troops have been battling Taliban attacks for months.

The Afghan military is currently rebuilding is main corps in Helmand, rotating in new leaders to deal with a range of problems from exhaustion to corruption.

The United States will add a battalion of troops with some advisers to its current deployment to the province, but will not be boosting troop numbers overall.

U.S. Army Col. Mike Lawhorn, spokesman for the U.S.-NATO mission in Afghanistan, said the incoming troops would be replacing an outgoing battalion from the same base. Lawhorn would give no further details on numbers. A battalion numbers up to 800.

The total U.S.-NATO deployment is around 13,000 troops, 9,800 of them from the United States, operating under the Resolute Support mission's "train, advise and assist" mandate.