The UN on Friday led condemnation of attacks by Islamic State jihadists on two sites in Syria's ancient city of Palmyra, calling the destruction a "war crime" and "cultural cleansing."
In a statement, Irina Bokova, director general of the Paris-based UN cultural agency UNESCO, described the wrecking as "a new war crime and an immense loss for the Syrian people and for humanity."
"This new blow against cultural heritage... shows that cultural cleansing led by violent extremists is seeking to destroy both human lives and historical monuments in order to deprive the Syrian people of its past and its future," Bokova said.
IS recaptured Palmyra, a UNESCO World Heritage site, from government forces on December 11 and the new devastation reportedly occurred earlier this month.
Syria's antiquities chief Maamoun Abdulkarim told AFP in Damascus earlier Friday that local sources said IS destroyed Palmyra's tetrapylon monument, while satellite images showed damage to the facade of the city's Roman amphitheatre.
The tetrapylon, built during the rule of the Roman Emperor Diocletian in the third century, consisted of four sets of four pillars each supporting massive stone cornices.
The monument had suffered considerable damage over the centuries and only one of the 16 pillars was still standing in its original Egyptian pink granite. The rest were cement replicas erected in 1963.
The Roman amphitheatre dates to the first century and was used by IS for public executions during its occupation of the city between May 2015 and March 2016.
The jihadist group had already ravaged the city during the nine months it held the site before being forced out of Palmyra in a Russian-backed offensive last March.
Moscow on Friday deplored the new destruction, with President Vladimir Putin's spokesman Dmitry Peskov calling it "a real tragedy from the point of view of cultural and historical heritage."
Asked whether the Russian military is likely to step in to recapture Palmyra for a second time, Peskov said only that: "Russian military continues to support the Syrians in battling terrorists."
- 'Barbarians' -
For his part, Russian Foreign Minister Sergei Lavrov, calling those who demolish world treasures "barbarians", added: "Such ideology and practice have absolutely no place in modern civilisation."
Also Friday, UNESCO said years of conflict in Syria had "totally destroyed" 30 percent of the historic Old City of Aleppo -- named a World Heritage Site in 1986 -- and around 60 percent of the quarter was "severely damaged."
The mission reported "extensive damage" to the Citadel, a fortress dating to the first millennium BC, and the Great Mosque of Aleppo, the largest and one of the oldest of the city's mosques.
The loss of east Aleppo was the biggest blow to Syria's rebel movement in the nearly six-year conflict, which has killed more than 310,000 people.
Last year International Criminal Court judges jailed a Malian jihadist for nine years for demolishing Timbuktu's fabled shrines in the first such case to focus on cultural destruction as a war crime.