BEIRUT (AFP) - The Islamic State in Iraq and Syria (ISIS) group captured a Jordanian pilot Wednesday after his warplane from the US-led coalition crashed while on a mission against the militants over Syria.

A senior Jordanian military official said the pilot was taken hostage by the "IS terrorist organisation" in its northern stronghold region of Raqa.

Both the militants and activists reporting to the Britain-based Syrian Observatory for Human Rights said the plane was hit by an anti-aircraft missile.

But the US military dismissed the claim, saying "evidence clearly suggests that ISIL did not down the aircraft", using another name for ISIS.

US Central Command, the body overseeing the coalition air war over Iraq and Syria, gave no reason for the "crash", and confirmed ISIS militants had taken the lost jet's Jordanian pilot captive.

The crash was the first coalition warplane lost since air strikes on ISIS began in Syria in September, and marks a major propaganda victory for the Sunni extremist group.

Coalition warplanes have carried out regular strikes around Raqa, which ISIS has used as its de facto capital since declaring a "caliphate" in June straddling large parts of Iraq and Syria.

ISIS posted photographs online purportedly showing its fighters holding the pilot.

One showed a man being carried from a body of water by four gunmen. Another showed the same man on land, surrounded by almost a dozen militants.

A photograph was also released of the pilot's military identification card, showing his name as Maaz al-Kassasbeh, his birth date as May 29, 1988, and his rank of first lieutenant.

The extremists claimed to have shot down the warplane with a heat-seeking missile.

Images distributed by ISIS supporters of the alleged aftermath of the crash appeared to show the distinctive canopy of an F-16 fighter jet.

The pilot's father, Youssef, was quoted by Jordanian media as saying the family had been informed by the air force of his capture.

He said the military promised it was "working to save his life" and that King Abdullah II of Jordan was following events.

An activist in Raqa said ISIS militants were divided over the fate of the pilot.

"The Chechens want him dead but the Iraqis want to keep him alive," Nael Mustafa told AFP via the Internet.

"For some time, there have been divisions among them over who should be in command."

The decision would be made by the shura, or council, representing all nationalities in ISIS, a Sunni extremist group that has committed widespread atrocities including mass executions and public beheadings.

UN Secretary-General Ban Ki-moon expressed concern and appealed for the pilot's captors to treat him humanely.

British Foreign Secretary Philip Hammond tweeted his support for the pilot.

"Concerned for Jordanian pilot held by ISIL. We stand with Jordan at this difficult time," Hammond wrote.

Jordan is among a number of countries that have joined the US-led alliance carrying out air strikes against ISIS.

Saudi Arabia, the United Arab Emirates, Jordan and Bahrain are taking part in the strikes in Syria alongside the United States.

Elsewhere in Syria, 10 people including six children were killed as they left rebel-held Zabdine in southeast Damascus for a regime area, said the Observatory.

In neighbouring Iraq, a suicide bomber killed at least 26 people and wounded dozens in an attack on Sunnis opposed to ISIS as they gathered to receive salaries south of Baghdad.

And in the northern city of Kirkuk, a gunman killed the head of the provincial counter-terrorism forces.

The US-led coalition first launched strikes against ISIS in August in Iraq, weeks after the jihadists overran the country's Sunni heartland.

The coalition said it had carried out 10 strikes on Wednesday in Syria, including one near Raqa, where the Jordanian jet crashed, and seven in Iraq.

Iraqi security forces, backed by the strikes, Kurdish forces, Shi'ite militias, and Sunni tribesmen, have retaken some areas, but have been facing stiff resistance from the entrenched ISIS militants.

Some Sunni militiamen have joined the fight against ISIS and Wednesday's attack near a military base in the Madain area targeted Sunni fighters known as Sahwa.

The Sahwa, or "Awakening" in Arabic, date back to the height of the US-led war in Iraq, when Sunni tribesmen joined forces with the Americans to battle insurgents including ISIS' predecessor organisation, the Islamic State of Iraq.