It also suggested that the Sinai-based militants are among the region’s most resilient, after IS in Iraq and Syria where the so-called caliphate is now witnessing its demise, and underscored the struggles the Egyptian forces face in trying to rein in the insurgency.

Egypt has for years battled militants in Sinai, where the jihadists have exploited the vast arid and underdeveloped region and its disgruntled Bedouin population as an ideal incubator for Islamic insurgency, but more recently, the IS affiliate had emerged at the forefront of the insurgency.

Friday’s assault began in the early morning, when a suicide bomber rammed his vehicle into a checkpoint at a military compound in the village of el-Barth, southwest of the border town of Rafah.

That was followed by dozens of masked militants who descended on the site in 24 Land Cruiser SUVs, and opened fire on the soldiers with machine guns, according to security officials.

The shooting lasted nearly half an hour, the officials added, speaking on condition of anonymity under regulations. The troops at the compound were estimated to have numbered about 60.

When the attack subsided, the militants apparently looted the checkpoint, snatching weapons and ammunition before fleeing the scene, the officials said. It was unclear if they also took armoured vehicles. A number of militants were killed in the shoot-out, indicating the soldiers had fought back, and some of their vehicles were left at the scene, abandoned.

The suicide blast at the start of the attack likely disabled the checkpoint’s military communications system, prompting an officer to use his own cellphone to record an audio message and send it to colleague via WhatsApp, seeking help and asking for prayers. The message, which was later widely circulated on social media, is said to belong to one of the five officers killed in the attack, identified as Lt Colonel Ahmed el-Mansi of the special forces.

“This might be the last seconds in my life,” a man’s voice calmly says in the recording. “Quickly, oh men, anyone who knows how to reach the command centre, notify them to use artillery as we are still alive.”

He then praises God and ends by saying “we will either avenge them or die,” referring to his fallen colleagues.

As the attack unfolded, ambulance sirens were heard from a distance rushing to the site. The security officials initially put the death toll at 10 but later said that more bodies were pulled from under the rubble of a nearby building, used as a rest house for troops, that was hit in the attack.

Earlier, Egyptian army spokesman Tamer el-Rifai confirmed the attack on his official Facebook page, saying that 26 army personnel were killed or wounded. He didn’t provide a breakdown.

He said the army on Friday foiled attacks that targeted a number of other checkpoints in the Rafah area and that 40 militants were killed. Local Sinai residents, speaking on condition of anonymity for fear for their safety, said that they saw Apache helicopters carrying out airstrikes across Rafah after the attack. On his page, al-Rifai posted photographs of allegedly slain militants, dressed in military uniforms, typically worn by IS extremists.

The Defence Ministry posted a video on its official website showing aircraft taking off and striking vehicles and positions allegedly belonging to the militants who carried out Friday’s attack.

The attacked checkpoint was set up two months ago to sever a key militant supply line between the outskirts of the town of Rafah, where entire neighbourhoods are known to have a heavy IS presence, and central Sinai, where militants have found safe havens in the mountains, according to tribal leader Hassan Khalaf of the Swaraka, one of Sinai’s largest tribes.

The restive northern Sinai has been under a state of emergency since October, 2014, after Islamic militants killed more than 30 soldiers in a single attack. There was a significant decline in attacks this year in Sinai, with the one major assault killing eight policemen in el-Arish in a car bomb in January.

On July 1, 2015, IS carried series of attacks, killing over 50 soldiers in Sinai. IS said at the time that it attacked some 15 army and police positions and staged three suicide bombings. However, the army denied the high death toll.

The Sinai attack came as IS militants are fast losing their once vast territory in Syria and Iraq.

Hamas, which is seeking to improve relations with Cairo, quickly condemned Friday’s attack.

“We considers it a criminal, terrorist, and coward attack that doesn’t target Egypt only, but the security and stability of the entire Arab nation,” Hamas’ spokesman Fawzi Barhoum said.