Israel's Prime Minister Benjamin Netanyahu spoke Thursday by telephone to King Abdullah II, the premier's office said, apparently their first contact since Jordan announced its ambassador was returning to Tel Aviv.

"Prime Minister Netanyahu extended his condolences to the King and to the Jordanian people" over the murder of a Jordanian air force pilot by the Islamic State group, a statement said.

Jordan said its warplanes launched new strikes Thursday against the Islamic State group, after vowing a harsh response to the burning alive of one of its fighter pilots captured in Syria.

The news came as scores of people were killed when rebels unleashed deadly rocket fire on the Syrian capital and President Bashar Assad's air forces and artillery retaliated.

Jordanian King Abdullah II personally paid his condolences Thursday to the family of the fighter pilot burned to death by the Islamic State group, after promising harsh revenge for his execution.

The king travelled to Karak, 120 kilometres (74 miles) south of the capital, the hometown of Maaz al-Kassasbeh, where a traditional mourning tent was set up for the family to receive guests, state television showed.

Hizbullah on Wednesday condemned as a “brutal crime” the execution by burning of Jordanian fighter pilot Maaz al-Kassasbeh at the hands of the Islamic State group, describing the IS militants as “butchers.”

“Hizbullah condemns the brutal, heinous crime that was committed by the IS gang against the Jordanian pilot,” the party said in a statement.

King Abdullah II vowed Jordan will take tough action after hanging two convicted militants Wednesday in response to the burning alive of one of its pilots by the Islamic State group.

The gruesome murder of airman Maaz al-Kassasbeh triggered international condemnation and prompted Jordan to execute two Iraqis on death row -- female would-be suicide bomber Sajida al-Rishawi and al-Qaida operative Ziad al-Karboli.

The Islamic State group's gruesome murder of a captured Jordanian pilot is the consequence of Amman's support for Syrian rebels, Syrian media said on Wednesday.

The commentary in newspapers close to the government echoed longstanding claims by President Bashar al-Assad's regime that Jordan is backing "terrorists" by supporting rebels.

Jordan executed two Iraqi jihadists, including a female would-be suicide bomber, on Wednesday in response to the burning alive of one of its fighter pilots by the Islamic State group.

The gruesome murder of airman Maaz al-Kassasbeh triggered condemnation from governments across the Middle East, while a top Muslim body called for the killing or crucifixion of IS militants.

The chief of the U.S.-led war on IS, General Lloyd Austin, condemned the pilot's murder as "savage" and vowed to "fight this barbaric enemy until it is defeated".

British Prime Minister David Cameron said the "sickening murder will only strengthen our resolve to defeat ISIL", another acronym for the group.

The Islamic State group released a video Tuesday purportedly showing a Jordanian pilot being burned alive in a cage, in the jihadists' most brutal execution yet of a foreign hostage.

The highly choreographed 22-minute video released online showed images of a man purported to be First Lieutenant Maaz al-Kassasbeh, captured in December, engulfed in flames.

Jordan on Monday sentenced two Syrians to three years in jail each after they were charged with plotting to kidnap a U.S. aid worker for ransom last year.

The state security court, a military tribunal, accused them of "terrorist activity" and sentenced them to three years' hard labor, said an AFP reporter in court.