Militants in Afghanistan opened fire with heavy weapons across the border at a Pakistani military outpost at night, killing three soldiers, the army said on Saturday, AP reported.

A firefight ensued with militants firing at an army post in Pakistan's North Waziristan region, and several people were killed, the statement said.

The incident comes amid a series of bombings in Afghanistan in recent days, including a mosque bombing in the northern province of Kunduz on Friday that killed 33 people, including several students from a nearby religious school.

The astonishing rise in attacks in Afghanistan - as well as in neighboring Pakistan - highlights the growing security challenge faced by the Taliban leadership in Afghanistan, who came to power last August in the final days of the chaotic US and NATO withdrawal that ended a 20-year war.