Here is a list of major Syrian historical sites or monuments destroyed in the country's nearly six-year-old war.
The UN cultural agency UNESCO has repeatedly denounced the "immense" damage caused to archaeological sites across the country.
The Association for the Protection of Syrian Archaeology (APSA) says hundreds of monuments and archeological sites have been looted, damaged or destroyed since the war began in March 2011.
- Palmyra -
The UNESCO-listed world heritage site located northeast of Damascus fell to the Islamic State jihadist group in May 2015. Syrian forces recaptured it in March 2016 but the jihadists retook Palmyra in December.
IS fighters have blown up famed tower tombs, targeting the first century AD monuments as part of a campaign to destroy the ancient site.
Among the tombs destroyed were the three best preserved and most treasured funerary towers, including the famed Tower of Elahbel.
IS condemns pre-Islamic religious works as idolatrous.
In July 2015, it destroyed the statue of the Lion of Athena, which stood more than three metres (10 feet) high in front of Palmyra museum.
Another masterpiece destroyed was the main Temple of Bel, which dated back 2,000 years.
In August 2015, the group murdered the 82-year-old retired head of antiquities in Palmyra, Khaled al-Assad, and hung his mutilated body in public.
On Friday, Syria's antiquities chief Maamoun Abdulkarim and UNESCO said IS had in its second occupation destroyed the tetrapylon, a 16-columned structure that marked one end of the ancient city's colonnade, and damaged the Roman amphitheatre.
Palmyra was also damaged in 2013 during fighting between rebels and government forces.
- Aleppo -
Aleppo, in northern Syria, is one of the world's oldest continually inhabited cities, dating back to at least 4,000 BC.
Syrian forces took full control of the city in December after more than four years of intense fighting with rebel groups that had split Aleppo in two.
In 2013, Aleppo's Old City was placed on UNESCO's list of endangered sites.
In September 2012, a blaze swept through ancient shops in the city's souk, or marketplace, and in April 2013, the minaret of the historic Omayyades mosque collapsed.
Rebels using explosives to reach government positions in the Old City destroyed the iconic Carlton Hotel on May 8, 2014.
In July 2015, a blast destroyed some of the ramparts that surround the citadel, a leading example of mediaeval Islamic military architecture.
A UNESCO report published on Thursday says: "According to a preliminary assessment, some 60 percent of the Old City of Aleppo has been severely damaged, with 30 percent totally destroyed".
- Crac des Chevaliers -
The heavily fortified Crusader fortress near Homs in central Syria known as the Crac des Chevaliers and used as a rebel base was damaged by army shelling.
- Maaret al-Numan -
On June 20, 2015, the best-known mosaic museum in Syria was seriously damaged by barrel bombs dropped by regime aircraft, the archaeology association APSA said.
- Raqa -
In IS's northern bastion, shrines dedicated to Uwais al-Qarani, renowned among Sufis, and Ammar bin Yasir, a companion of the Prophet Mohammed, have been destroyed, with NGOs blaming jihadists.
In the northeastern region of Hasakeh, IS has also destroyed Assyrian statues dating from the first century, APSA said.
Other notable sites damaged or looted include Dura-Europos, Apamea, Ebla, Mari, Ajaja and Hamam Turkoman.