KABUL- Hundreds of Pakistani families have fled from a surge of fighting between Pakistani government forces and militants into neighboring Afghanistan, an Afghan government official said today.

The government forces have been launching air strikes against Pakistani Taliban fighters in a northwestern valley near the Afghan border in recent days, after Taliban fighters raided the country's biggest airport, in Karachi, late on Sunday.

Missile-firing U.S. drone aircraft have also, for the first time in six months, attacked militants this week in Pakistan's North Waziristan region, a lawless militant stronghold on the Afghan order.

Millions of Afghan civilians have for decades sought shelter in Pakistan to escape war in their homeland but the fighting in Pakistan this week has sparked a rare flow of civilians the other way.

"Around 300 Pakistani families have escaped because they are worried about fighting between Pakistani forces and Pakistani Taliban," said Jabar Nahimi, governor of eastern Afghanistan's Khost province, over the border from northwest Pakistan.

Both Afghanistan and Pakistan are facing threats from al Qaeda-linked Taliban factions but relations between the neighbors are more often marked by mutual suspicion, and even hostility, rather than cooperation on security.