Pakistan has reportedly fired warning shots at US-led helicopters, repelling them as they entered the country's tribal region.

"The US-led coalition troops in helicopters came close to the border and they tried to enter into Pakistan territory in the early hours of Monday but shots were fired by Pakistani troops and the coalition troops retreated," AFP quoted a security official as saying Monday.

The incident took place near Angor Adda village in South Waziristan, where US troops carried out a heli-borne raid earlier this month and killed at least 20 people including women and children.

Pakistani Army Chief General Ashfaq Kayani had earlier warned that Islamabad would not tolerate border violations by US troops stationed in Afghanistan, adding that his country will not accept foreign troops on its soil.

In recent months, there has been an increase in Washington-led missile strikes in Pakistan's tribal areas. While the US claims the strikes have been directed at militants, it has killed scores of civilians in missile attacks this year and has sparked outrage in Pakistan.

Pakistani officials and tribal leaders have also threatened to retaliate should US cross-border attacks continue.

HE/AA/BGH