NATO-led peacekeepers in Afghanistan on Saturday blamed militants for a mortar attack two nights earlier that wounded Pakistani soldiers and Afghan police on either side of the border and led to a Pakistani protest.

"Insurgents simultaneously fired at targets in Afghanistan and Pakistan on the evening of July 10," said a statement from the International Security and Assistance Force (ISAF) headquarters in Kabul.

ISAF said it had reports four Afghan police and eight Pakistanis were wounded in the two-way attack, and added that it suspected the insurgents' aim was "to spark a border incident".

The clash occurred on the border near the Pakistani village of Angor Adda in the South Waziristan tribal region, a known sanctuary for al Qaeda and Taliban militants.

Angor Adda lies across the border from Berman, a village near a U.S. base at Shikin in Afghanistan's Paktika province.

The peacekeepers said ISAF's retaliatory air and artillery strikes did not touch Pakistani territory.

"ISAF forces tracked the fire to two points within Afghanistan and returned fire with artillery and one GBU-13 bomb dropped from an F-15 aircraft," the statement said.

"All ISAF rounds were verified to have hit the origins of insurgent fire."

Pakistani troops had also returned fire after coming under a mortar attack that wounded six soldiers and two civilians, a Pakistani military spokesman said.

He did not say if U.S.-led coalition or Afghan forces fired mortars but added that a "strong protest" had been lodged with the headquarters of the coalition forces in Kabul on Friday.

The latest incident comes at a time of increased tension between Pakistan and Afghanistan.

Also, there are growing fears in Pakistan, a key ally in the U.S.-led war on terrorism, that the United States is planning to mount operations inside its territory.

Afghan officials say there have been more attacks inside Afghanistan after the Pakistan military reached a de facto truce with militants based in Pakistan tribal areas.

The militants had unleashed a wave of attacks across Pakistan over the past year.

After coming to power in March the new Pakistani government led by the party of assassinated former Prime Minister Benazir Bhutto tried to quell the violence by using tribal intermediaries to hold a dialogue with Taliban factions.

Militant leaders suspect the Pakistan army is using the breathing space to prepare a fresh offensives against them.

At the same time, Pakistani tribesmen have reported increased sightings of pilotless U.S. drones over the frontier.

U.S. drones have struck several times in northwest Pakistan this year, killing dozens of suspected militants.

Last month, Pakistan was outraged when 11 soldiers were killed in a U.S. air strike ordered after coalition forces came under fire from militants in Pakistan's Mohmand tribal region.