MIRAMSHAH Pakistani troops twice opened fire to repel two US helicopter gunships which violated Pakistani airspace in a tribal region bordering Afghanistan, officials said on Monday.

The incidents happened about half an hour apart on Sunday evening near Lwara Mundi village in the North Waziristan district, where Pakistani forces have been battling Taliban and al-Qaeda militants, they said.

'Pakistani forces fired at two US gunships which violated Pakistan's airspace and forced them to return to Afghanistan,' a local security official told AFP.

'The helicopters flew back after our troops fired shots at them.'

A senior security official based in Islamabad said later that the helicopters were repelled on two separate occasions by both army troops and soldiers from the paramilitary Frontier Corps (FC).

'The helicopters were heading towards our border. We were alert and when they were right on the boundary line we started aerial firing, they hovered for a few minutes and went back,' the official said.

'About 30 minutes later they made another attempt. We retaliated again, firing in the air and not in their direction, from both the army position and the FC position, and they went back,' he added.

There was no immediate comment from the Pakistani military or the US-led coalition in Kabul.