Reports say the soldiers were killed early Saturday after a joint Afghan-International Assistance Force operation against Taliban insurgents received gunfire from the direction of a Pakistani border post and called in airstrikes.
Islamabad called the airstrikes by jets and helicopters "unprovoked," a violation of national sovereignty, and immediately retaliated: Two border crossings used by ISAF convoys carrying supplies to coalition troops in Afghanistan were closed, stranding some 300 vehicles.
About 40-50 percent of non-lethal supplies -- including fuel -- for international forces in Afghanistan pass through the Torkham crossing in the northwest Khyber tribal area of Pakistan and Chaman, in southwestern Baluchistan province.
Pakistan also ordered the United States to vacate within 15 days an airbase in the country that U.S. forces use for servicing unmanned aerial vehicles that conduct surveillance and attack missions against Afghan insurgents in the ill-defined border areas.
"The attack was unprovoked and indiscriminate," said Pakistani army spokesman Maj. Gen. Athar Abbas. "There was no reason for it. Map references of all our border posts have been passed to NATO a number of times."
The Pakistanis say the outpost was clearly marked, had a flag flying and that no gunfire came from it or the surrounding area.
Predictably, anti-U.S. and anti-NATO demonstrations erupted throughout Pakistan, where anger is ever-present over continued American UAV strikes in Pakistan's border tribal areas against Taliban insurgent hideouts and over Washington's unilateral raid on the Pakistan hideout of al-Qaida leader Osama bin Laden in May.
Although Pakistan is an ally in the war against terrorism and is itself targeted by Islamist extremists, it is accused of turning a blind eye to Taliban groups that fight in Afghanistan but use Pakistan's border areas as safe havens. Earlier this year, outgoing Chairman of the U.S. Joint Chiefs of Staff Adm. Michael Mullen publically said he believed Pakistan's powerful intelligence service gives aid to Afghan insurgents fighting the United States, NATO and the Kabul government.
The public accusation, together with the bin-Laden raid, has brought U.S.-Pakistan relations to its lowest ebb.
NATO called the airstrike Saturday a "tragic, unintended incident" and has launched an investigation into it. U.S. Secretary of State Hillary Clinton and Defense Secretary Leon Panetta apologized for the incident and expressed condolences to the families of the dead Pakistani soldiers. They also supported the NATO investigation.
"My most sincere and personal heartfelt condolences go out to the families and loved ones of any members of Pakistan security forces who may have been killed or injured," added U.S. Marine Corps Gen. John Allen, commander of NATO forces in Afghanistan.
But Pakistani sensitivities are unlikely to be soothed any time soon and meanwhile tons of supplies used by U.S. and coalition forces in Afghanistan are sitting in trucks at vulnerable crossing points along the Pakistan-Afghan border.
Insurgents last year blew up more than 100 convoy vehicles at the border while they were waiting to cross.
It is believed the delay in transporting the supplies won't affect ISAF forces for the time being. They have reportedly stockpiled enough non-lethal supplies to last several months. But if Pakistan were to permanently sever the links, then U.S. and NATO forces would have to rely on the northern supply route that passes through Russia and Central Asia.
Lethal equipment -- munitions, for example -- wouldn't be affected since they are flown into Afghanistan.
Pakistan once before closed a border crossing to NATO after two of its soldiers were killed by a U.S. helicopter but soon reopened. A joint Pakistan-U.S. investigation determined the Pakistanis had fired at the helicopter, possibly as a warning to the aircraft that it had strayed into Pakistani territory.
Ironically, Allen had met the day before the latest incident with Pakistani Chief of Army Staff Gen. Ashfaq Pervez Kayani over border-control issues.
Coalition troops frequently complain of receiving fire from insurgents on the Pakistani side of the Afghan border. Whatever the outcome of the latest incident, with the end of NATO presence in Afghanistan still years away, Saturday's incident is unlikely to be the last.