ISLAMABAD, Aug. 24 (Xinhua) -- United States gunship helicopters Monday violated the international border and intruded into Pakistani territory, official sources said.

    Sources told the local NNI news agency that the helicopters entered northwest Pakistani airspace at 0835 GMT at Khyber tribal region.

    The gunship helicopters crossed into Pakistani air space for a kilometer, flying for five minutes and went back to Afghanistan, officials said.

    The unexpected intrusion by U.S. helicopters spread fear among the local residents, NNI said.