Islamabad: Mortar shells fired from Afghanistan wounded six Pakistani security forces along the border, and Pakistan has lodged a "strong protest" with Nato, the army's top spokesman said.

The six mortars were fired overnight on Friday and fell close to a military post in the town of Angore Adda in the South Waziristan tribal region, Major General Athar Abbas said. Pakistani forces immediately returned fire, and "casualties were reported on the other side," he said.

"This was mortar fire from the Afghan side," Abbas said. "Whether it was foreign forces or Afghan forces it's yet
to be determined."

Asked if militants across the border could have been behind the firing, Abbas said he did not want to speculate. US military officials in Afghanistan did not immediately respond to requests for comment.


The clash comes about a month after another border incident in which Pakistan said 11 of its soldiers died when US aircraft bombed their post in the Mohmand area.

US officials have said coalition aircraft dropped bombs during a clash with militants. Though they expressed regret over the incident, they said the action was justified.