UN Secretary-General Ban Ki-moon has said he is appalled by reports that self-styled Islamic State militants had demolished a temple in Syria's ancient Palmyra.
IS fighters packed explosives in the Baal Shamin temple and blew up the shrine on Sunday, Syria's antiquities chief said.
Mr Ban also voiced outrage over the murder of Khaled al-Assaad, the retired chief archeologist at Palmyra, whose body was mutilated after he was beheaded on 18 August.
"These barbaric acts of terror join a long list of crimes committed over the past four years in Syria against its civilian population and heritage," Mr Ban said in a statement.
Palmyra is listed as a world heritage site by the UN cultural body UNESCO, and Mr Ban recalled that destroying world cultural sites was a war crime.
The UN chief called on world governments to "unite and act swiftly to put a stop to this terrorist activity."
The temple bombing is the first time the insurgents, who control swathes of Syria and Iraq and captured Palmyra in May, damaged monumental Roman-era ruins.
Before the city's capture by Islamic State, Syrian officials said they moved hundreds of ancient statues to safe locations out of concern that the militants would destroy them.
In June, IS militants blew up two ancient shrines in Palmyra that were not part of its Roman-era structures but which the militants regarded as pagan and sacrilegious.
UNESCO chief Irina Bokova said the destruction of the temple was a "war crime" and added the "perpetrators must be accountable for their actions".
