Pakistan says seven soldiers have been beheaded by Islamist militants who infiltrated from Afghanistan, lashing out at Kabul over cross-border attacks.
The protests come with Pakistan under growing US pressure to act against al-Qaeda-linked safe havens on its own soil and the anti-terror Islamabad-Washington alliance at its lowest ebb since the 9/11 attacks.
Pakistan already reported that six soldiers were killed in gunbattles with militants on Sunday who crossed from Afghanistan into the northwestern district of Upper Dir, a key border transit route that neighbours the Swat valley, where Pakistan defeated a local Taleban insurgency in 2009.
Intelligence officials blamed the attack on loyalists of Pakistani cleric Maulana Fazlullah, who fled to Afghanistan after losing control of Swat to the army.
But on Monday, the military said 11 soldiers went missing in the same incident, "of whom seven soldiers have been reportedly killed and then beheaded".
The bodies have not been found, but intelligence intercepts indicated they had been killed, a senior military official told AFP.
The army said more than 100 militants "from a safe haven across the border" attacked troops on patrol. It claimed to have killed 14 militants.
Pakistan said two rockets and sniper fire were also fired into Lower Dir on Monday.
The army "has strongly protested with their counterparts across the border for not taking action against miscreants present in safe haven in Afghanistan", a military official said.
Pakistan's new prime minister also condemned the attacks and said he would discuss the matter with President Hamid Karzai.
Pakistani troops have been bogged down for years fighting local Taleban but have resisted US pressure to carry out a sweeping offensive against Afghan Taleban fighters.