A US F-15E fighter has been shot down over Iran, prompting a frantic US search and rescue effort for its two-strong crew, in the first such incident since the start of the war.

Images of a tail fin and other debris were released by Iranian state media early on Friday accompanied by an initial claim that an advanced US F-35 and been hit by a new air defence system over central Iran and the pilot probably killed.

Aviation experts said the wreckage pictured was in fact from a F-15E from the US air force’s 494th squadron, based at RAF Lakenheath in the UK, though it could not at first be confirmed when and where the pictures were taken.

US officials familiar with the situation later confirmed off the record that an F-15E had been brought down and the Pentagon was scrambling to find the crew. But there was no official comment from the US military about the incident.

Subsequent footage filmed from Iran showed a US C-130 Hercules and HH-60 Pavehawk helicopters flying low and at one point refuelling together, accompanied by fresh Iranian speculation that the plane crew may have ejected and survived.

Justin Bronk, an aviation expert from the Royal United Services Institute (Rusi), said the use of the specialist helicopters “suggested a combat search and rescue mission is underway to locate and extract the two aircrew from the F-15E”.

A social media account claiming to be linked to Iran’s Revolutionary Guards posted a picture of an ejector seat in a desert landscape, which appeared to be consistent with the ACES II type used in F-15Es. “If genuine it would suggest that at least one of the two aircrew did eject safely,” Bronk added.

The presenter on an Iranian TV channel urged residents to hand over any “enemy pilot” to police and promised a reward for anyone who did.

Iran’s Tasnim news agency reported that the pilot of the jet – still incorrectly describing it as an F-35 – had been taken into custody, contradicting Tehran’s initial claim that the pilot had probably died in the incident.

Overnight, the US Central Command, which is leading the attack on Iran, had denied Iranian claims that another F-35 jet had been downed over Qeshm Island in the strait of Hormuz. “All US fighter aircraft are accounted for,” it said at the time.

Up to now no US fighter jets had been lost over Iran during the five-week-long conflict, though three F-15Es were shot down by a Kuwaiti air defence system in a friendly fire incident on 1 March.

An F-35 fighter reportedly had to make an emergency landing at a US airbase in the Middle East after sustaining damage from the ground. A US E-3 Sentry airborne warning and control system aircraft was destroyed at the Prince Sultan airbase in Saudi Arabia on 27 March in an Iranian strike.