AMMAN (REUTERS) - Jordanian fighter jets pounded Islamic State hideouts in Syria on Thursday and then roared over the hometown of a pilot killed by the militants, while below them King Abdullah consoled the victim's family.

Witnesses overheard the monarch telling the pilot's father the planes were returning from the militant-held city of Raqqa.

A security source told Reuters the strikes hit targets in the eastern province of Deir al-Zor and near Raqqa.

The show of force came two days after the ultra-hardline Islamic State in Iraq and Syria (ISIS) released a video showing captured Jordanian pilot Muath al-Kasaesbeh being burned alive in a cage as masked militants in camouflage uniforms stood around watching.

State television said details of the attacks would be made known later.

If so, this would be the first time Jordan has announced carrying out strikes outside the framework of the US-led military coalition ranged against Islamic State.

A US official, speaking to Reuters on condition of anonymity, said that the strikes took place in the vicinity of Raqqa, where the Jordanian pilot was executed.

Military commanders briefed King Abdullah after the missions about the details of the strikes, state television said.

The monarch has vowed to avenge Kasaesbeh's killing and ordered commanders to prepare for a stepped-up military role in the US-led coalition against the group.

But many Jordanians fear being dragged into a conflict that could trigger a backlash by hardline militants inside the kingdom.

Jordan is a major US ally in the fight against hardline Islamist groups, and hosted US troops during operations that led to the invasion of Iraq in 2003.

It is home to hundreds of US military trainers bolstering defences at the Syrian and Iraqi borders, and is determined to keep the militants in Syria away from its frontiers.

'NO HUMANITY'

State television showed a sombre King sitting alongside the army chief and senior officials visiting the Kasaesbeh tribal family in Aya, a village some 100km south of the capital Amman.

The King, wearing a traditional Arab head dress, was met with cheering crowds and cries of "Long Live his Majesty the King, Long Live the King" in traditional Bedouin chanting.

Thousands of Jordanians flocked to pay their respects in a part of the country where influential tribes form an important pillar of support for the Hashemite monarchy and supply the army and security forces with their manpower.

"You are a wise monarch. These criminals violated the rules of war in Islam and they have no humanity. Even humanity disowns them," Safi Kasaesbeh, father of the pilot, told the King.

The Jordanian monarch has vowed that the death of the pilot, which has stirred nationalist fervour across the country, will bring severe retaliation against Islamic State.

Hours after the release of the video showing the pilot burning to death, the authorities executed two Al-Qaeda militants who had been on death row, including a woman who had tried to blow herself up in a suicide bombing and whose release had been demanded by Islamic State.