The 11th-century minaret of a landmark mosque in Aleppo was destroyed, leaving the once-soaring stone tower a pile of rubble and twisted metal scattered in the tiled courtyard.
President Bashar al-Assad's regime and rebels traded blame for the destruction to the Umayyad Mosque, a Unesco World Heritage site in the heart of Aleppo's walled Old City. Mosques served as a launching pad for anti-government protests in the early days of the country's two-year uprising, in which the United Nations says more than 70,000 people have been killed.
Meanwhile, the European Union's counter-terrorism chief warned that Europeans travelling to Syria to join the rebels could return and pose a threat back home, echoing concerns in Belgium where the government is mulling intercepting aspiring fighters at airports.
Fears are growing throughout Europe that impressionable young Muslims could come into contact with Islamist factions of the opposition. Al-Qa'ida-linked groups are known to operate on the fringes of the movement to oust President Assad.
The Netherlands has raised its terror alert to "substantial", citing fears people returning from Syria could plot attacks, while Belgian police last week raided dozens of homes across the country to crack down on the networks recruiting potential fighters.
"Not all of them are radical when they leave, but most likely many of them will be radicalised there," Gilles de Kerchove told the BBC in an interview. "As we've seen this might lead to a serious threat when they get back."
He estimated 500 Europeans were in Syria fighting with the rebels while UK officials have said up to 100 British Muslims have gone there to fight.