BEIRUT (Reuters) - Satellite images have confirmed the destruction of the Temple of Bel, which was one of the best preserved Roman-era sites in the Syrian city of Palmyra, a United Nations agency said, after activists said the hardline Islamic State group had targeted it.

Combination picture shows the site of the Temple of Bel before (top) and after its apparent destruction in Palmyra, Syria, in this August 27, 2015 and August 31, 2015 handout satellite images provided by UrtheCast, Airbus DS, UNITAR-UNOSAT. REUTERS/UrtheCast, Airbus DS, UNITAR-UNOSAT/Handout via Reuters

A comparison of before and after images shows the damage to the temple at the UNESCO World Heritage site, the Geneva-based United Nations Institute for Training and Research (UNITAR) said.

“We can confirm the destruction of the main building of the Temple of Bel as well as a row of columns in its immediate vicinity,” the agency said in an email.

The Syrian Observatory for Human Rights monitoring group and other activists said on Sunday that Islamic State had destroyed part of the more than 2,000-year-old temple, one of Palmyra’s most important monuments.

This came a week after the militants blew up another smaller site in the central desert city.

Palmyra was one of the most important cultural centers of the ancient world, according to cultural agency UNESCO, which has described it as the crossroads of several civilizations. Its main colonnaded street is 1 kilometer (0.6 miles) long and forms the monumental axis of the city.

The head of UNESCO said in a statement the destruction of what it described “as one of the most important 1st Century religious monuments in the Middle East,” was an “intolerable crime against civilization”.

“The power of culture is greater than that of all forms of extremism and nothing can stop it,” Director-General Irina Bokova said.

“Whoever saw Palmyra remains forever marked by the memory of the city which embodies the dignity of the entire Syrian people and humanity’s loftiest aspirations,” she added.

Information on events inside Palmyra has been patchy since the militants seized it from government forces in May. Activists say the fighters are closely monitoring communications inside the city.

Islamic State has declared a caliphate in territory it holds across Syria and Iraq and has destroyed other monuments it says are pagan and sacrilegious.

UNESCO has called such acts war crimes and says Islamic State seeks to wipe out evidence of Syria’s diverse heritage.

Before the capture of the city, Syrian officials said they had moved hundreds of ancient statues to safe locations.

Last month Islamic State beheaded the guardian of Palmyra’s ruins, Khaled al-Asaad, an 82-year-old Syrian archaeologist who had looked after the site for more than four decades, according to Syria’s antiquities chief.