ISLAMABAD, Sept. 15 (Xinhua) -- Pakistan's security forces and Afghanistan-based U.S.-led coalition forces clashed along the Pakistani-Afghan border on Monday, the state-run PTV reported.

    Some U.S spy and fighter planes violated Pakistan's airspace at the Angor Ada area of South Waziristan tribal region and returned to Afghanistan after action from Pakistan's security forces, said the report.

    The News Network International (NNI) news agency quoted locals as saying that a U.S. fighter plane was sighted in the area, forcing Pakistan's border troops to blow warning siren from bunkers. Fierce firing was also heard in the area, according to NNI.

    On the weekend, Pakistan, for the first time, sent fighter planes to the Waziristan tribal region to check any airspace violation by the U.S. planes, according to local tribesmen.

    The tribal areas especially Waziristan region have witnessed missile attacks launched from suspected U.S. drones. Pakistan has lodged strong protests against the cross-border attacks.