The mother of a Lebanese soldier held captive by the militant Islamic State group said photographs posted online claiming to show his beheading appear to be real.
Zeinab Noun said her 20-year-old son, Abbas Medlej, was "sacrificed" after supporters of the militant group posted images appearing to show a captured Lebanese soldier before and after he was beheaded.
"My son was sacrificed," said Ms Noun, clutching a passport-sized photo of her son.
Mr Medlej's maternal uncle, Abu Ali Noun, also said the photographs appeared to be of his nephew. A spokesman for Lebanon's military said it was still investigating the incident.
Mr Medlej would be the second captive Lebanese soldier killed by the Islamic State group, underscoring the grave challenges that face the ill-equipped Lebanese military as it fends off an unprecedented jihadi threat from Syria-based militants.
Around two dozen more members of the country's security forces remain held captive by militants. They were seized in August when several groups, including the Islamic State group and Nusra Front, overran a Lebanese border town, killing and kidnapping soldiers and policemen in the most serious spillover yet of the neighbouring civil war.
Families of the captive soldiers have blocked roads and held demonstrations to pressure the Lebanese government to negotiate with the militants.
Local media had reported that negotiations were under way, with the militants demanding cash and the release of Islamists being held in Lebanese detention. A statement posted by supporters of the Islamic State said Mr Medlej was killed after he tried to escape.
He hailed from a large Shiite clan from the eastern Lebanese city of Baalbak.
His mother vowed revenge on rival Sunnis. "We have to take our revenge from those apostates," she said.
The captured soldiers and police are from Lebanon's many religious sects including Sunni Muslims and Christians.
IN April of last year, in the beleaguered town of Harem in north-west Syria, they had the audacity to hope. Vicious fighting between rebels and pro-government troops in the preceding months had seen the population drop from 25,000 to just 1,000, as people fled or were killed.