The militants' attacks, launched in the wee hours of Monday on security checkpoints in Bala Duri and Baba Nazar areas in the outskirts of Pul-e-Khumri, triggered gun battle during which four policemen were killed and eight others injured, deputy of the provincial council Shamsul Haq Barikzai said.
Police have confirmed the fighting but declined to provide more details, Xinhua news agency reported.