An Egyptian jihadist group on Thursday released a video in which it claimed responsibility for beheading four men accused of being "Israeli informants" before showing the victims' decapitated bodies.

In the video, terrorists belonging to Ansar Beit al-Maqdis, considered the deadliest jihadist group in Egypt, say they killed the men in the restive Sinai Peninsula for assisting neighboring Israel.

Their bodies were found in Sheikh Zuweid town on August 20, two days after they were abducted, security officials said.

The footage shows the kidnapped men confessing to assisting Israel in a drone strike in July that killed three terrorists near the border with the Jewish state. At the time, Egypt's military said it had killed the extremists.

After the confession, a masked man reads a statement that threatens Israel and its "collaborators".

He begins to cut the victims' necks before they are then shown dead, with their disembodied heads placed on their backs.

The group is believed to have carried out its first beheading in 2012 – kidnapping and murdering a man they accused of assassinating a terrorist.

Ansar Beit al-Maqdis – "Partisans of Jerusalem" in English – has claimed a number of high-profile attacks in Sinai, the Nile Delta, and Cairo since Islamist president Mohamed Morsi was overthrown in July 2013. It has sworn allegiance to the Islamic State.

Egypt's military has carried out a vast offensive against jihadist groups in the north of Sinai since militants stepped up attacks following Morsi's ouster.

Ansar Beit al-Maqdis has said its operations are in retaliation for the brutal government crackdown on Morsi's supporters that left more than 1,400 dead and at least 15,000 imprisoned.

It has also claimed several rocket attacks against Israel over the past two years.