"Pakistani officials have accused Nato helicopters of firing on a military checkpoint near Pakistan's Afghan border, killing 26 soldiers.
The "unprovoked and indiscriminate" attack took place in the Pakistani tribal region of Mohmand, the Pakistani military said in a statement.
In response, Pakistan has closed the border crossing for supplies bound for Nato forces in Afghanistan.
Nato said it was aware of "an incident" near the border and was investigating.
The alleged attack took place at the Salala checkpoint, about 1.5 miles (2.5 km) from the Afghan border, Reuters reports, at around 02:00 local time (21:00 GMT).
Two officers were among the dead, officials said, and seven soldiers were reported wounded."
The "unprovoked and indiscriminate" attack took place in the Pakistani tribal region of Mohmand, the Pakistani military said in a statement.
In response, Pakistan has closed the border crossing for supplies bound for Nato forces in Afghanistan.
Nato said it was aware of "an incident" near the border and was investigating.
The alleged attack took place at the Salala checkpoint, about 1.5 miles (2.5 km) from the Afghan border, Reuters reports, at around 02:00 local time (21:00 GMT).
Two officers were among the dead, officials said, and seven soldiers were reported wounded."