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.

Saudi Arabia's new King Salman on Wednesday called the burning alive of a Jordanian fighter pilot "inhuman and contrary to Islam".

In a message of condolence to Jordan's King Abdullah II, he said the kingdom "learned with profound sadness of the martyrdom of Maaz al-Kassasbeh".

Dirt-covered skulls and bones scattered among ragged clothing in a ditch in north Iraq are all that remain of some two dozen people believed to have been murdered by the Islamic State group.

The blood still staining one side of the ditch and the bullet casings scattered on the ground paint a grim picture of how they died.

An Egyptian court Wednesday sentenced to life 230 secular activists from the 2011 revolt against long-time strongman Hosni Mubarak, including leading campaigner Ahmed Douma, an official said.

Thirty-nine others, all minors, were jailed for 10 years. 

By burning a Jordanian pilot alive in its most savage execution video yet, the Islamic State (IS) group aims to terrify its Arab and Western opponents into ending their anti-jihadist war.

Already infamous for beheading and stoning to death its victims, IS is trying to "up the ante" with the latest execution, experts said.

Nearly 1,000 Iraqi Kurdish peshmerga fighters have been killed battling the Islamic State jihadist group since June, a senior security official said on Wednesday.

Jabbar Yawar, the secretary general of the ministry responsible for the peshmerga, told a news conference that 999 Kurdish fighters were killed and 4,569 wounded between June 10 and February 3.

Saudi Arabia beheaded two convicted rapists and a murderer on Wednesday, the interior ministry said, bringing to 21 the number of people it has executed so far this year.

The three were all Saudis.

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.

Al-Azhar, Sunni Islam's most prestigious centre of learning, expressed outrage Wednesday at the Islamic State group for burning to death a captive Jordanian pilot, saying its militants deserve to be killed or crucified.

After a video was released showing the caged fighter pilot, Maaz al-Kassasbeh, dying engulfed in flames, the Cairo-based authority's head, Ahmed al-Tayib, expressed his "strong dismay at this cowardly act".

The United Arab Emirates pulled out of the air campaign fighting Islamic State militants after the capture of a Jordanian pilot who has since been killed by the extremists, the New York Times reported Wednesday.

The pilot was captured in December and Islamic State militants released a video Tuesday showing the man in a cage being burned alive.