Beirut: Military helicopters have tried to land, under heavy covering fire, in the de facto capital of radical Islamist militants in Syria in a dramatic hostage rescue effort, local activists have reported.

If confirmed, the night raid in Raqqa, which was aborted when the helicopters came under attack, may have been an attempt by members of the US-led coalition forces to rescue a Jordanian pilot being held by the Daesh.

Lieutenant Mua’th Al Kasasbeh was captured when his plane crashed near Raqqa last month, and has been threatened with execution by Daesh.

Activists from the group Raqqa Is Being Slaughtered Silently posted details of Thursday’s attack on their website. The group, which operates in secret inside the city, was the first to break the news of a failed rescue mission led by US special forces last July. In details later confirmed by the Pentagon, the group accurately reported the location and strategy of that raid.

Thursday’s raid involved heavy bombardment across the city and military clashes as decoys, the group said. “In the hours before, drones were flying over Raqqa,” said Abu Ebrahim Al Raqqawi, a spokesman who has now left the city. “Then there was the heaviest bombardment of the city since the start of air strikes by the coalition.”

An air strike reportedly destroyed a building used as a barracks by Daesh fighters. Jets were also flying in an area west of the city centre before clashes broke out on the ground, Al Raqqawi said. “I have friends in the area. They saw what was happening from their rooftop and then had to take cover. There was an exchange of gunfire for 20 minutes, and someone was firing flares to light the sky.” This may have been a rescue mission, or a decoy for the military operation on the other side of the city, he speculated.

In eastern Raqqa two helicopters were “making an attempted landing”, he said. “Daesh started shooting at them and they had to abort.” He said a mole in Daesh had told him of the attack, and had confirmed that the helicopter landing was taking place in the area where Lieutenant Kasasbeh was being held.

This newspaper cannot independently confirm the details. The US-led coalition declined to comment on whether there had been a raid or rescue mission. A spokesman said: “We have received no information to confirm or refute this event took place.”