Nato helicopters have fired on a military checkpost near Pakistan's Afghan border, killing up to eight soldiers, say Pakistani officials. A military spokesman said the attack had taken place in the Pakistani tribal region of Mohmand. Nato said it was aware of "an incident" near the border and that it was investigating. The Pakistani military said it was an "unprovoked and indiscriminate" attack. "Casualties have been reported and details are awaited," a military spokesman said. The alleged attack took place at the Salala checkpost, about 1.5 miles (2.5 km) from the Afghan border, Reuters reports, at around 02:00 local time (21:00 GMT). Pakistani troops are involved in fighting the Taliban in the crucial border region area. Some 5,000 militants have been resisting attempts by the security forces to clear them from southern and south-eastern parts of the district. The US has been targeting militants in Pakistan's tribal areas near the Afghan border for several months. Last year, US helicopters accidentally killed two Pakistani soldiers near the border, prompting Pakistan to temporarily close the border to supplies shipped through the country to Nato troops in Afghanistan. In October, Pakistan's army chief Ashfaq Kayani warned the US against taking unilateral action in nearby North Waziristan. He said that the US should focus on stabilising Afghanistan instead of pushing Pakistan to attack militant groups in the crucial border region. Washington has for many years urged Islamabad to deal with militants in the area. BBC News - Nato helicopters 'attack Pakistan checkpoint' Is this new beginning???