France has identified a second national who appeared unmasked in the latest execution video released by the Islamic State of Iraq and the Levant (ISIL) armed group, and announced it was sending more fighter jets to the region to step up air strikes.

Several ISIL fighters appeared unmasked in the latest execution video which showed the killing of at least 12 Syrian prisoners and a US aid worker Peter Kassig.

One foreigner, 22-year-old Maxime Hauchard from Normandy in northern France, was quickly identified by French prosecutors.

On Wednesday, French prosecutors said there was "precise and consistent evidence" that a second national in the video was 22-year-old Mickael Dos Santos from an eastern Paris suburb, who goes by the name Abu Uthman.

Dos Santos, of Portuguese origin but born in the French riverside town of Champigny-sur-Marne, is believed to have left for Syria in the autumn of 2013.

French intelligence was made aware of him after he published an online video in October calling for "all brothers living in France" to "kill any civilian" in retaliation for air strikes carried out by Paris against ISIL in Iraq.

"The man concerned is known for his terrorist involvement in Syria and his violent behaviour shown on social networks," French Prime Minister Manuel Valls said, without confirming his identity.

Air force boosted

French authorities estimate around 1,000 nationals have taken part in the conflict, with 375 currently in the country.

Valls said "close to 50" French citizens had been killed in Iraq and Syria.

"So we know the dangers and, sadly, we are not surprised to learn that French citizens or residents of France are found at the heart of these cells and taking part in this barbarity."

Meanwhile, French Defence Minister Jean-Yves Le Drian announced on Wednesday that six Mirage fighter jets would be sent to Jordan in December to boost air forces in their campaign against the group.

He said French aircraft in Iraq had pummelled trenches used by ISIL fighters around the northern Iraqi city of Kirkuk on Tuesday night.

Currently France is using nine Rafale jets based in the more distant United Arab Emirates as part of a US-led coalition to provide air support to Iraqi and Kurdish forces fighting the group.

ISIL has carried out widespread atrocities since seizing control of large parts of Iraq and Syria, executing hundreds of locals and five Western hostages.

Source: Agencies