A fighter from the Islamist Syrian rebel group Jabhat al-Nusra is seen in front of a burning vehicle.
A fighter from the Islamist Syrian rebel group Jabhat al-Nusra is seen in front of a burning vehicle..Reuters

A day after a Nusra Front commander threatened to retaliate against Lebanon for holding his wife and children captive, a captive Lebanese soldier was killed by the militants on Friday.

Abu Ali al-Shishani, commander of the Al-Qaeda-backed Nusra Front has issued a warning to Lebanon after Lebanese authorities detained his wife and two children, who are reportedly being kept with Saja al-Dulaimi, belived to be ISIS leader Abu Bakr al-Baghdadi's wife.

The group posted a video on Friday, in which it claimed that it had murdered Lebanese policeman Ali Bazzal in retaliation to the detention of Shishani's wife Ola Mithqal al-Oqaily.

The group has threatened to execute another captive if the women held captive by Lebanese officials are not released.

"If the sisters that were unjustly arrested are not released, then after a short period of time the death sentence will be executed against another prisoner we hold. We will not accept anything but the release of all our women and children... one of my children is 4 years old, the second is less than 6 months old. How dare you arrest them with their mother?," Shishani said in the new video, Al Jazeera reported.

More than 30 Lebanese people are under the captivity of militants of the Nusra Front and the Islamic State after a border raid in August.

Shishani's wife is reportedly in a prison cell at the Lebanese Defence Ministry along with al-Dulaimi, who has been the focus of media speculations over her alleged identity as Baghdadi's estranged wife.

Lebanon erupted in protests on Saturday following news of the killing.