The US-based coalition has killed a senior Islamic State group facilitator in an air strike in the extremists' self-proclaimed capital of Raqa, the US military command in the region said Friday.

CENTCOM identified the target as Mahmud al-Isawi, an IS operative who managed instructions and finances for IS leaders and provided propaganda and intelligence support.

He was killed on December 31, making him the 16th significant member of the network's external operations killed last year.

The longtime IS member provided to the group's media and intelligence in Fallujah prior to his move to Raqa.

He also facilitated transregional travel with other IS operators and had what CENTCOM dubbed a "close working and personal relationship" with Abd al-Basit al-Iraqi, emir of the group's Middle East attack network who was slain in a coalition air strike on November 2.

"His death, combined with the recent successive deaths of other ISIL leaders plotting terrorist attacks, has degraded ISIL's trans-regional attack and facilitation network, and is forcing ISIL to increase their focus on internal security," CENTCOM said.

"The coalition will continue to track and eliminate ISIL terrorists who plot and conduct attacks against coalition nations and our allies, wherever they are hiding."

Syria has been wracked by a devastating civil war for nearly six years that has killed more than 312,000 people and forced millions to flee their homes.