ISLAMABAD, Aug. 21 (Xinhua) -- At least two policemen were killed and another was injured when some unknown militants opened fire at a police check post here on Wednesday night, the additional deputy commissioner (ADC) of Islamabad told Xinhua.

The militants opened fire at the check post near a vegetable market at the outskirts of the city and fled the scene, ADC Waseem Khan said.

"One policeman was killed right at the spot and two others got injured who were shifted to a hospital in Islamabad where one of them succumbed to injuries."

The official said that the cause of the firing is being ascertained by collecting evidence from the site. However, no group or individual has claimed responsibility yet.