Director-General of Unesco Irina Bokova on Tuesday "expressed profound dismay" and condemned the destruction of the temple of Bel in Syria's Palmyra.
She said the site was "a construction unique in design and one of the most important 1st century religious monuments in the Middle East", Xinhua reported.
"The destruction of Palmyra constitutes an intolerable crime against civilisation but 4,500 years of history will never be erased," Bokova was quoted as saying.
"The power of culture is greater than that of all forms of extremism and nothing can stop it," she stressed, calling to "share ever more widely the heritage of humanity, whether in museums, schools, the media and our homes."
On Sunday, the Islamic State (IS) terrorists blew up the temple of Bel with tons of explosives, the Islamist group's second major destruction of the most important sites in the antiquities of Palmyra since its fighters seized the city in May.
Last month, the IS detonated the temple of Baal Shamin.
"It is essential to explain the history and significance of the temples of Palmyra. 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," Bokova said.
