ISIL, has destroyed other parts of the Palmyra area including two shrines in June, and the grave of Mohammad Bin Ali, a descendant of Imam Ali, cousin of Islam's Prophet Muhammad.. Reuters

The courtyard of the sanctuary, part of the ruins of ancient city of Palmyra which was declared a UNESCO World Heritage Site in 1980. Joseph Eid / AFP / Getty Images

A relief depicting the sun and an eagle with a laurel branch in its beak was integrated into the temple’s architrave. DeAgostini / Getty Images

A view of the interior of the temple, which dates to 17 AD. Reuters

The Temple of Baal Shamin in Palmyra was blown up by ISIL. DeAgostini / Getty Images

The demolition of a renowned ancient temple in the Syrian city of Palmyra by the Islamic State in Iraq and the Levant (ISIL) is a war crime that targeted a historic symbol of the country's diversity, the United Nations cultural agency UNESCO said on Monday.

ISIL fighters blew up the Roman-era temple of Baal Shamin on Sunday, said Syria's antiquities chief Maamoun Abdulkarim. The temple was one of the most important sites in the central Syrian desert city.

"Such acts are war crimes and their perpetrators must be accountable for their actions," UNESCO Director General Irina Bokova said in a statement.

She also condemned the killing of Khaled al-Asaad, an 82-year-old archaeologist who had looked after Palmyra's UNESCO World Heritage ruins for four decades.

Abdulkarim said last week that ISIL had beheaded Asaad and hung up his body in public. Before ISIL captured the city, Syrian officials said they moved hundreds of ancient statues to safe locations out of concern that ISIL would destroy them.

ISIL, which holds parts of Syria and Iraq, seized the desert city of Palmyra in May from government forces but had initially left its ancient sites undamaged.

In June ISIL blew up two shrines that were not part of the city’s Roman-era structures, but which the group regarded as sacrilegious. ISIL had also used Palmyra's Roman amphitheater as a place for killing people it accused of being government supporters, according to a Syria monitoring group.

The Baal Shamin temple was built nearly 2,000 years ago and its inner area was severely damaged by the explosion, which also caused surrounding columns to collapse, according to UNESCO.

"The art and architecture of Palmyra, standing at the crossroads of several civilizations, is a symbol of the complexity and wealth of the Syrian identity and history," Bokova said. "Extremists seek to destroy this diversity and richness, and I call on the international community to stand united against this persistent cultural cleansing."

Reuters