The US said Thursday (May 28th) it would offer up to $3 million for the arrest of a senior leader of the "Islamic State of Iraq and Syria" (ISIS) who has overseen the extremists' grisly execution videos.

The State Department said it would provide the reward in return for information on the location or further identification of Jordanian-born Muhammad Khadir Musa Ramadan, also known as Abu Bakr al-Gharib.

"He has overseen the planning, co-ordination and production of numerous propaganda videos, publications and online platforms that included brutal and cruel scenes of torture and mass execution of innocent civilians," it said in a statement.

Ramadan also has led an effort to "cleanse ISIS of moderate opinions, imprisoning members of ISIS's propaganda teams who did not meet his extreme interpretation of Islam", according to Rewards for Justice website.

In mid-May, a 50-minute video produced by ISIS began to circulate on extremist social media accounts.

It contained a compilation of clips that show various attacks ISIS elements carried out in the preceding weeks in Iraq.

It showed the execution of unarmed tribesmen in northern and western Iraq, the burning of wheat fields and orchards, the bombing of electricity pylons and the shooting of livestock.

There also were scenes of improvised explosive devices (IEDs) detonating, sniper operations and armed attacks against Iraqi security forces, and of civilians being beheaded under various pretexts.

US special forces in October killed the group's leader Abu Bakr al-Baghdadi inside Syria, where the extremists once ran a self-styled "caliphate" that stretched into Iraq.

The extremists carried out summary beheadings and enslaved non-Muslims, with videos of their deeds used to recruit fighters from around the world.