Both US-led NATO coalition forces and Taliban insurgents operating across the border have used mortars as part of combat operations in the nine-year war and neither side was immediately available to comment on the attack.

"Five mortar shells fired from the Afghan side landed in Teti Madakhel village," in the Mir Ali district of North Waziristan region late Thursday, a military official said.

He said the mortars hit houses located just three kilometres from the border.

"As a result, five civilians -- three women and two men -- were killed and six injured," he said.

The injured were confirmed by a doctor at the nearby state-run hospital in Mir Ali.

Intelligence officials in the region's main town Miranshah confirmed the mortar attack and said it came from the neighbouring Afghan province of Khost.

A NATO spokesman in Kabul said the alliance force was looking into reports of the shelling but had no immediate information.