More than 100 Islamist fighters have been killed by US air strikes on a training camp in Syria as American forces expand their assault beyond Isis.

The Department of Defense said planes and drones were involved in Thursday’s operation on the Shaykh Sulayman camp in northern Syria, on the last day of Barack Obama’s presidency.

A statement described the target as an “al-Qaeda training camp”, but monitors say it was controlled by Jabhat Fateh al-Sham (JFS) and Hakarat Nour al-Din al-Zenki.

JFS claimed it split from al-Qaeda last year, when it changed its name from Jabhat al-Nusra, while the Nour al-Din al-Zenki movement received American weapons including TOW anti-tank missiles as one of dozens of “vetted groups”.

Its fighters filmed themselves beheading a Palestinian boy accused of spying last year, and has abducted and tortured journalists and humanitarian workers.

Captain Jeff Davis, a spokesperson for the Pentagon, said the camp had been operational since at least 2013.

“The removal of this training camp disrupts training operations and discourages hardline Islamist and Syrian opposition groups from joining or cooperating with al-Qaeda on the battlefield,” he added.

Fighting continues in Syria as al-Nusra breaks from al-Qaeda

The US extended air strikes from Iraq into Syria in 2014, followed by other members of the coalition including Britain, with the stated aim of targeting Isis.

But the bombing campaign has been increasingly expanding to include al-Qaeda linked groups including JFS, which has been gathering power and territory across Syria while international efforts have focused on its rival Isis.

More than 150 al-Qaeda militants have been killed so far this year, the Pentagon said, including several high profile leaders and militants plotting terror attacks in the West.

“These strikes, conducted in quick succession, degrade al-Qaeda’s capabilities, weaken their resolve, and cause confusion in their ranks,” Mr Davis said.

JFS released a statement condemning the strike and accusing the US of aiding Bashar al-Assad’s regime, which Mr Obama’s administration opposed.

Reports on jihadi Telegram channels said the joint training camp was “preparing dozens of Mujahideen for the coming battle against regime forces and Shia militias”.

The targeted camp is in a region expected to be a key battleground for Bashar al-Assad’s forces (AP)

They claimed at least 110 “martyrs” had been killed, publishing graphic footage showing body parts strewn amid the rubble of the destroyed camp.

An official, speaking to Reuters on condition of anonymity, said the strike was carried out by a B-52 bomber and unmanned aircraft that dropped 14 munitions.

The camp, near the border between Aleppo and Idlib province, is in a region expected to be the Syrian President’s next target following his force’s assault on rebel-held parts of Aleppo city.

Civilians were allowed to cross into government-controlled areas, while fighters fled to the east into regions controlled by JFS and other Islamist and opposition rebels.

The UK-based Syrian Observatory for Human Rights said JFS and al-Zinki fighters were killed by drone at a joint camp known as Regiment 111, although it was unclear whether the report referred to the same attack.

Islamist activists accused the US of injuring children and civilians in recent strikes, including one on a car carrying a high profile militant, showing a young boy in hospital.

British jets prepare for air strikes in Syria Show all 10 1 /10 British jets prepare for air strikes in Syria British jets prepare for air strikes in Syria A Tornado jet takes off from RAF Lossiemouth in Scotland, as RAF Tornado jets carried out the first British bombing runs over Syria British jets prepare for air strikes in Syria Pilots and ground crew prepare combat aircraft Panavia Tornados at RAF Marham at RAF Marham, UK Getty British jets prepare for air strikes in Syria A Eurofighter Typhoon jet takes off from RAF Lossiemouth in Scotland, as RAF Tornado jets carried out the first British bombing runs over Syria British jets prepare for air strikes in Syria A RAF Tornado arrives at RAF Akrotiri to begin operations in Akrotiri British jets prepare for air strikes in Syria A Tornado jet ahead of taking off from RAF Lossiemouth in Scotland, as RAF Tornado jets carried out the first British bombing runs over Syria, the Ministry of Defence has confirmed. The air strikes were carried out within hours of a vote by MPs in the Commons to back extending operations against Isis from neighbouring Iraq British jets prepare for air strikes in Syria Personnel work on a British Tornado after it returned from a mission at RAF Akrotiri in southern Cyprus British jets prepare for air strikes in Syria Two RAF Tornado GR4's, both with remaining weapons ordnance, approach RAF Akrotiri in Cyprus, as they return to the base after carrying out some of the first British bombing runs over Syria British jets prepare for air strikes in Syria A RAF Tornado takes off from RAF Akrotiri, on the Mediterranean island nation of Cyprus British jets prepare for air strikes in Syria A Tornado jet leaving RAF Lossiemouth in Scotland British jets prepare for air strikes in Syria AKA RAF Tornado arrives at RAF Akrotiri to begin operations in Akrotiri, Cyprus. The RAF has sent two further Tornado aircraft and six Typhoons to bolster aircraft now flying sorties to both Iraq and Syria

American probes have so far confirmed at least 188 civilians killed in bombing in Syria and Iraq, with several other incidents still ongoing.

Air strikes continued on Friday, with Isis militants, vehicles, oil wells, weapons and infrastructure targeted in the Raqqa, Deir Ezzor and Homs provinces of Syria, as well as near Mosul, Kisik and Kirkuk in Iraq.

US-led forces carried out a three-day campaign to prevent Isis transporting fighters and equipment across the Tigris River in Mosul, where they have been driven out of eastern parts by Iraqi security forces.

Coalition planes struck 90 watercraft and three barges, Central Command said.

“We believe this was a desperate attempt to retrograde Isil (Isis) fighters now that the Iraqi Security Forces own the eastern bank of every bridge in Mosul,” said Col John L Dorrian.

The US has hailed vast territory losses by Isis after using its firepower to back partner forces on the ground in operations to retake strongholds including Fallujah and Jarablus.