The IS group is not the only extremist group to carry out brutal execution-style killings.
Al-Qaeda militants in Yemen have stoned a woman to death in the southwestern Yemeni city of Mukalla after accusing her of adultery, witnesses say.
One witness said the militants "placed the woman in a hole in the middle of the courtyard of a military building and stoned her to death in the presence of dozens of residents."
A small boy who appeared on a new IS killing video alongside a British-accented IS militant has been confirmed as Isa Dare, the son of Grace Dare, a British woman who went to Syria in 2012.
The child's grandfather Henry Dare confirmed to The Telegraph that the young boy in the video is his grandson.
The child is shown in IS's latest execution-style killing video saying that militants will kill "unbelievers."
All oil terminals are under the control of Libya's Petroleum Facilities Guard, tweets Digital Libya's Sami M. Berriwen.
But the militants are reportedly mobilizing their forces 30 kilometers away from Sirte for a second attack on the oil terminals, Berriwen says.
The presidential council of Libya's unity government has met to discuss the situation in Libya's oil crescent region after today's attacks by the IS group, Al Wasat is reporting.
More reports that IS has now retreated back towards Sirte after being pushed back from Sidra by the Petroleum Facilities Guard (PFG).
Syria's opposition are demanding confidence-building steps from Damascus including a prisoner release before negotiations due this month, officials have told Reuters. Three opposition leaders said that they and rebels plan to deliver that message to Staffan de Mistura, the U.N.'s envoy for Syria, on January 5.
The demand "could complicate efforts to start the talks," Reuters reports.
CBS News is quoting Ali al-Hassi, a spokesman for the armed forces led by Ibrahim al-Jadhran that control most of Libya's oil fields, as saying that six of their fighters were killed in today's clashes with IS militants in Sidra.
IS militants reportedly attacked Sidra from three directions, assisted by Jadhran's brother who is believed to have joined IS.
Jadhran, who took part in the rebellion against Muammar Qaddafi in 2011, has declared himself the guardian of Libya's oil crescent.
The Petroleum Facilities Guard (PFG), whose forces pushed IS militants back from Sidra in Libya today, have said that IS are now stationed 30 kilometers away waiting for the opportunity to launch a second attack on Libya's biggest oil port.
The PFG are led by Ibrahim al-Jadhran, a former commander who took part in the rebellion against Muammar Qaddafi in 2011.
A storage tank that caught fire when IS militants attacked the Libyan oil port of Sidra today was close to the oil port of Ras Lanuf, Mohamed Elharari, a spokesman for the state-run National Oil Corp, has told Bloomberg.
“An oil storage tank caught fire and there was a big explosion,” Elharari said.
The IS group in Libya has released images of its militants who it says were killed carrying out suicide attacks today in Sidra.