PUL-E-KHUMRI, Afghanistan, Aug. 23 (Xinhua) -- Three police officers were killed in two separate attacks in northern Afghanistan on Thursday, local police said.

"Mohammad Salim, chief of criminal investigation department of Nahreen district, Baghlan province, was killed and two of his brothers critically wounded, following a Taliban militants' ambush attack Thursday morning," Zabihullah Shuja, provincial police spokesman, told Xinhua.

The incident took place in the strategic Charshanba Tapa area, bordered with northern Kunduz province, he said, adding a probe was underway.

In the neighboring Badakhshan province, unknown gunmen killed two policemen guarding the Badakhshan University in the provincial capital of Faizabad city, and took away their arms early Thursday, Sanaullah Ruhani, provincial police spokesman, told Xinhua.

Fighting has escalated in Afghanistan as the Taliban insurgency spreads from its traditional strongholds in the south and east to the once peaceful region in the north, where the Taliban militants have been recruiting fighters among the youth.