Wednesday's raid was the first confirmed groundoperation by foreign troops based in Afghanistan and it dominated theagenda in Pakistan's parliament.
Foreign Minister Mahmood Qureshi said the government had already summoned the U.S. ambassador to complain.
Hesaid the operation was shameful because it violated the sovereignty andterritorial integrity of a U.S. ally in the war against terrorism.
Detailsabout the raid remain unclear, including who was behind it. Westernnews agencies have reported that U.S. military sources claim Americantroops based in Afghanistan carried out the assault on a village lessthan two kilometers from the Afghan border. The number of peoplereported killed varied from seven to 20 and Pakistani officials saidnearly all of them were civilians.
Pakistan's military hasworked with U.S. and NATO forces in Afghanistan for several years toestablish guidelines governing military action along their sharedborder.
Pakistan army spokesman Major General Athar Abbas said Wednesday's operation was an unprecedented violation of those guidelines.
"Inthe past the other side, NATO ISAF, have been engaging the foreignmilitants present in the area and on this actionable intelligence theyengage them through their Predators [drones]," he said. "But neverbefore did a single incursion take place, which has seriousconsequences."
The cross-border operation follows months ofincreased violence in eastern Afghanistan. U.S. commanders have blamedsafe havens in Pakistani tribal areas for giving militants space tore-arm and plan attacks.
But Major General Abbas saidWednesday's assault was especially worrying because there were noreports of militants in the area. He said such operations riskedalienating local tribes whose support is vital for defeating Talibanmilitants.
"We do not want this line which is dividing themilitant component and the tribe at large to diminish," he said."Because if it gets obliterated where the tribe and the militant joineach other - and there is an uprising against the local security forcesor the forces from outside - this would create one big problem."
TopPakistani and U.S. commanders met on an aircraft carrier in the IndianOcean last week to discuss border security. Major General Abbasinsisted the officials did not authorize cross-border ground assaultssuch as Wednesday's raid in South Waziristan.