Peace talks between the Pakistan government and the local Taliban have suffered a setback after a government committee cancelled a scheduled round of negotiations over the reported execution of 23 soldiers in the fighters' captivity.
The cancellation of Monday's planned talks appeared to cast doubt over a dialogue just two weeks after it began.
A faction of the Tehreek-e-Taliban Pakistan (TTP) from the northwestern district of Mohmand announced late on Sunday that it had killed the soldiers, who it said had been kidnapped in 2010.
"We captured [the soldiers] in June 2010, and we killed all 23 soldiers," Umar Khurasani, TTP's Mohmand Agency spokesman, said. "We are going to decide whether to be part of these talks or not."
It was not immediately clear whether the faction acted with the approval of the Pakistani Taliban central command.
Government negotiators declared the talks to be "purposeless" after the "sad and condemnable" murders, while Pakistan President Mamnoon Hussain expressed "grief and sorrow".
"We regret to say that things are not moving in a right direction," Irfan Siddiqui, chief government peace negotiator, said in a statement.
He said a meeting would be convened on Tuesday to discuss the future course of action.
The government's committee was scheduled to meet a committee responsible for negotiating for the fighters at a seminary in Pakistan's northwest.
"If they [government committee] are not here, then what you will call it? This is called deadlock," Mohammad Ibrahim, one of the Pakistani Taliban Committee members, said.
In a statement on Monday, Nawaz Sharif, Pakistan's prime minister, condemned as "heinous" the reported executions.
"Such incidents have an extremely negative impact on the ongoing dialogue aimed at promoting peace," he said.
Sharif said Pakistan "cannot afford such bloodshed" and lamented that previous attempts to start dialogue were "sabotaged whenever it reached an encouraging stage".
He announced the start of talks with the TTP on January 29 to "give peace another chance" following a seven-year insurgency that has claimed nearly 7,000 lives.
The TTP's Mohmand Agency faction said the executions were in revenge for government forces killing their members.
The Associated Press news agency reported in June 2010 about claims by fighters that they had kidnapped 35 Frontier Corps troops in the area.
It was not immediately clear whether this was the same group of soldiers and if so, why the numbers were different.
As part of the negotiations, a member of the Pakistani Taliban negotiating team recently travelled to North Waziristan to meet the group's leaders and then convey their demands to the government.
Monday's talks were due to be held in the northwestern town of Akora Khattak, where Mullah Omar, the Afghan Taliban chief, and his other high-level commanders are said to have studied
Critics of the peace process say the fighters have broken several such agreements in the past and simply used them to strengthen their organisation and regroup.