ISIS militants in the ancient Syrian city of Palmyra. Screenshot The Syrian army announced on Sunday that it had recaptured the ancient city of Palmyra, with the aid of Russian air support, from the Islamic State.

ISIS fighters seized Palmyra in May 2015, immediately raising concerns that the group would destroy the city's antiquities and artifacts that date back to the first century.

The group is known to loot and destroy ancient sites for both religious and financial purposes, and soon after the capture of Palmyra, the fears of historians and preservationists were realized by reports of destruction across the city.

As the city was being retaken, Syria's head of antiquities, Mamoun Abdelkarim, told Reuters that Syria hoped to restore stolen artifacts and reconstruct what had been destroyed.

"We will rebuild them with the stones that remain, and with the remaining columns," Abdelkarim said. "[We will] bring life back to Palmyra."

The work of assessing the scale of the damage can begin in earnest now that the city is back under Syrian control, though the damage is already known to include a triumphal arch, two temples, and funeral towers — destruction that UNESCO's Director-General Irina Bokova called an "immense loss."

UNESCO and Syrian antiquity authorities would enter the city to evaluate the damage and "protect the priceless heritage of the city of Palmyra, crossroad of cultures since the dawn of humanity," Bokova added.

She also noted that "UNESCO will do everything in its power to document the damage so that these crimes do not go unpunished."

Images of the city that the Islamic State left behind have continued to emerge as officials and journalists re-enter the city.