A group calling itself the Mohmand agency Taliban, reported to be opposed to the ongoing peace talks among negotiators from the Pakistani government and the Tehreek-i-Taliban Pakistan, claimed Sunday it had killed the 23 Pakistani Frontier Corps soldiers abducted in 2010.
Local media reports quoted the group's head, Umar Khalid Khurrasani, as saying in a letter issued through the social media that the captives were killed to avenge what Khurrasani said were the killings of incarcerated Taliban fighters in various parts of Pakistan.
Prime Minister Nawaz Sharif, whose government initiated the peace talks with the TTP, condemned the killings of the soldiers as a "heinous and brutal" act, and warned the incident would negatively impact the peace talks, the state-run Associated Press of Pakistan reported.
"Pakistan cannot afford such bloodshed," Sharif said. "However whenever we reach an encouraging point, the process is sabotaged."
The peace talks scheduled for Monday were called off.
The Daily Times reported the killing of the soldiers would be a major blow to Sharif's government, which has said the peace talks are a last chance effort to end the wave of Taliban violence in the past seven years in which hundreds of people and security personnel have been killed.
Irfan Siddiqui, who leads the four-member government negotiating committee at the peace talks, told reporters: "We do not want to play meetings," adding the killings of the soldiers cannot be tolerated.
"We regret to say that things are not moving in the right direction. Peace talks are purposeless after the sad and condemnable murders," the Daily Times quoted Siddiqui as saying.
He said the two sides were to meet Tuesday to decide the future course of action.
Another negotiator said it had not been confirmed whether the TTP had any role in the execution of the soldiers or if it was an attempt to sabotage the talks.
Another government negotiator said the way to salvage the talks would be for the TTP to dissociate itself from the statement of Khurrasani, the Daily Times said.
Dawn newspaper said the Pakistani army called the killings a "highly provocative act".
The army also rejected the claims that Taliban fighters were being killed while in detention, saying it was a "mere propaganda to justify their [Taliban's] dastardly acts of terror."
Separately, a TTP spokesman was quoted as telling Dawn in a telephone interview that his group wants sincere and serious talks with the government.
The spokesman said the TTP would contact the Mohmand group to get more details about the reported killings.
Prime Minister Sharif has said he is optimistic about the outcome of the peace talks, calling them a last chance to save the country from terrorism. He also said his government will not allow the country to be held hostage by them.
Prior to the offer of talks, there had been rumors the government was considering a major military offensive against the militants. Some analysts have said Pakistan's new military chief has favored using force against the militants.