BAGHDAD - Iraq announced Friday it had carried out air strikes against the Islamic State group in Syria, the third cross border aerial operation inside a month in its war-torn neighbour.

"Iraqi F-16 planes carried out (Thursday) morning raids against the headquarters of IS terrorist gang leaders and an explosives depot occupied by terrorists in Syria's Hajin region," a statement by Iraq's operations command said.

A video released with the text shows a strike on a huge building surrounded by palm trees and a wall.

The images show the wall and the building collapsing simultaneously.

Several strikes have been carried out by Iraq or the international coalition since Thursday against the centre of Hajin, the last major area held by IS in Syria, said the Britain-based Syrian Observatory for Human Rights war monitor. At least 65 senior IS leaders live in Hajin, the Observatory's director Rami Abdel Rahman told AFP.

Hajin is in Deir Ezzor province in eastern Syria, about 50 kilometres (just over 30 miles) from Iraq's border.

It has been surrounded since the end of 2017 by the Syrian Democratic Forces, an alliance of Kurdish and Arab fighters backed by the United States and France, Abdel Rahman said.

Several hundred prisoners are still held by the jihadists in Hajin, he added.

Since April, Iraq's air force has carried out several air strikes on IS-held Syrian territory close to the border between the two countries.

IS seized a third of Iraq in 2014, before the government declared victory in December, but the military has continued regular operations along the porous Syrian border.