Fighters from the Islamic State in Iraq and the Levant (ISIL) have beheaded a renowned antiquities scholar in the ancient Syrian city of Palmyra, seemingly after they failed to extract information from him regarding the whereabouts of hidden artifacts.

Syrian state antiquities chief Maamoun Abdulkarim said the family of Khaled Asaad had informed him that the 82-year-old scholar who worked for over 50 years as head of antiquities in Palmyra was executed by ISIL on Tuesday. Photos of the archaeologist's body hanging from a lamppost in the city have since circulated online. Asaad had been detained and interrogated for over a month by the Sunni Muslim armed fighters, Abdulkarim said.

ISIL, which controls swaths of Syria and Iraq, captured Palmyra in central Syria from government forces in May, but is not known to have damaged its monumental Roman-era ruins, despite the group's reputation for destroying artifacts it views as idolatrous under its interpretation of Islam.

A Palmyra-based Syrian opposition activist who uses the name Khaled al-Homsi and who identified himself also as a nephew of Asaad told the Associated Press that ISIL fighters detained the scholar about three weeks ago.

On Tuesday, they brought him in a van to a square packed with shoppers and read out five ISIL charges against Asaad — including that he was the "director of idols," represented Syria "at infidel conferences" and visited Shia powerhouse Iran — before he was executed.

Abdulkarim said Asaad was known for several scholarly works published in international archaeological journals on Palmyra, where antiquity flourished as an important trading hub along the Silk Road.

He also worked over the past few decades with U.S., French, German and Swiss archaeological missions on excavations and research in Palmyra's famed 2,000-year-old ruins, a UNESCO World Heritage Site including Roman tombs and the Temple of Bel.

Since ISIL overran Palmyra in May, there have been fears that fighters, who have destroyed famed archaeological sites in Iraq, would demolish the 2,000-year-old Roman-era city at the edge of the town — a UNESCO world heritage site and one of the Middle East's most spectacular archaeological sites.

Before the city's capture, Syrian officials said they moved hundreds of ancient statues to safe locations out of concern they would be destroyed by ISIL fighters. ISIL tried to extract information from Asaad about where some of the town's treasures were hidden, Abdulkarim said.

In June, ISIL blew up two ancient shrines in Palmyra that the fighters reportedly regarded as pagan and sacrilegious; the shrines were not part of the city's Roman-era structures.

Al Jazeera and wire services