A second Lebanese soldier taken hostage by Islamic State (IS) militants has been beheaded, reports say.
Photos of the killing of the soldier - named as Abbas Medlej - were posted on social media networks.
The Lebanese military said it was investigating the reports.
Abbas Medlej was among a number of Lebanese soldiers seized by IS in August, after the militants launched an incursion into the Lebanese town of Arsal, near the Syrian border.
Some of the hostages are reportedly being held by IS and others by the al-Qaeda-linked Nusra Front.
IS earlier threatened to kill a soldier every three days if the Lebanese government did not agree to release the group's members detained in Lebanese jails.
Abbas Medlej's mother, Zienab Noun, said the pictures showing the beheading appeared to be real.
"My son was sacrificed," she was quoting as saying by the Associated Press news agency.
On Saturday Islamic State issued a statement saying the soldier had been beheaded after he tried to escape.
Last week, the Lebanese army received the remains of a missing solider believed to have been beheaded by IS militants.
Officials said the body of Sgt Ali Sayyed was handed over to the Lebanese Red Cross outside Arsal.
A video purportedly showing Sgt Sayyed being decapitated was also posted online.
The fighting in Arsal - which left 16 civilians, 20 soldiers, and dozens of militants dead - was the most serious incident along the border with Syria since the uprising against President Bashar al-Assad began in 2011.
IS militants - who control large swathes of Syria and Iraq - have recently beheaded two American journalists, James Foley and Steven Sotloff.