Islamic State extremists have blown up the ancient temple of Baal Shamin in the UNESCO-listed Syrian city of Palmyra, the country's antiquities chief says.
"Daesh placed a large quantity of explosives in the temple of Baal Shamin today and then blew it up causing much damage to the temple," said Maamoun Abdulkarim, using another name for IS.
IS controls huge swathes of Syria and neighbouring Iraq, and captured Palmyra on May 21.
The fall of the city sparked international concern about the fate of the heritage site, described by UNESCO as of "outstanding universal value".
"The cella (inner area of the temple) was destroyed and the columns around collapsed," Abdulkarim said.
"Our darkest predictions are unfortunately taking place."
The Syrian Observatory for Human Rights, a Britain-based group that monitors the country's civil war, confirmed the destruction of the temple.
Baal Shamin was built in 17 AD and it was expanded under the reign of Roman emperor Hadrian in 130 AD.
Known as the "Pearl of the desert", Palmyra, which means City of Palms, is a well-preserved oasis 210 kilometres northeast of Damascus.
Its name first appeared on a tablet in the 19th century BC as a stopping point for caravans travelling on the Silk Road and between the Gulf and the Mediterranean.
But it was during the Roman Empire - beginning in the first century BC and lasting another 400 years - that Palmyra rose to prominence.
IS mined the ancient site in June before destroying the Lion Statue of Athena - a unique piece made of limestone that stood more than three metres high outside a museum.
Funerary busts were also destroyed by IS in Palmyra.
IS's harsh version of Islam considers statues and grave markers to be idolatrous, and the group has destroyed antiquities and heritage sites in territory under its control in Syria and Iraq.
The latest developments come just days after IS beheaded the 82-year-old retired chief archaeologist of Palmyra.
On Sunday the family of Khaled al-Assaad said the jihadists had mutilated his body after killing him execution-style on Tuesday.