Satellite images have confirmed the destruction of a Roman-era temple in the Syrian city of Palmyra, a United Nations agency said, after the hardline Islamic State group claimed responsibility for blowing up the structure a week ago.

The Islamic State group detonated explosives in the ancient Baal Shamin temple on Aug. 25, an act that cultural agency Unesco has called a war crime aimed at wiping out a symbol of Syria's diverse cultural heritage.

An analysis of an image taken in June and others taken several days ago show the obliteration of the temple in the central desert city, the Geneva-based United Nations Institute for Training and Research said in a statement.

"We confirm the destruction of the main building, while surrounding columns seem to be less affected."

Activists have said Islamic State is tightly controlling communications in the city, making its reports of events difficult to verify independently.

Islamic State has proclaimed a caliphate to rule over all Muslims from territory it holds in both Syria and Iraq. It has often carried out mass killings in places it captures and demolishes monuments it considers sacrilegious.

Islamic State published a photo report of the destruction on Tuesday. The group also beheaded Khaled al-Asaad, an 82-year-old Syrian archaeologist who had looked after Palmyra's ruins for four decades, and hung his body in public, according to Syria's antiquities chief.

The group seized the desert city of Palmyra in May from government forces but initially left its historical sites unharmed.

(Reporting by Sylvia Westall; Editing by Ruth Pitchford)