Two gunmen shot a Muslim cleric to death inside a mosque in southern Afghanistan, an official said Tuesday, while a NATO serviceman was killed elsewhere in the south.

The two men drove up to the mosque in Kandahar city on a motorcycle Monday night, shot the cleric, then drove off, said Zulmai Ayubi, a spokesman for provincial Gov. Tooryalai Wesa. The attackers have not been identified.

It was the second such incident in the area in less than two weeks. The head of one of Kandahar's main mosques was recently shot to death by gunmen while sitting inside the mosque.

Ayubi said both incidents were under investigation, and it was unclear if the attackers were Taliban or people angered or insulted by the clerics in some way.

Separately Tuesday, a NATO serviceman was killed in a "hostile incident" in southern Afghanistan, the International Security Assistance Force reported. NATO didn't release any more information, such as the soldier's nationality or the precise location of the incident.

On Monday, Taliban fighters attacked a police checkpoint south of Kandahar city, killing three officers in the ensuing gunfight, regional Police Chief Ghulam Ali Wahadkt said.

He said another officer was wounded and three were missing after the morning clash. Wahadkt said they did not have any information on Taliban casualties.