ISIS forces have retaken the ancient city of Palmyra in Syria, according to Syrian government media, the ISIS media wing and a human rights monitor.
Syrian news agency SANA reported that over 4,000 militants swarmed the city from "various directions," despite having suffered heavy losses from bombardments by the Syrian air force. The Russian Defense Ministry had earlier reported that its aircraft had also taken part in the air campaign.
The UK-based Syrian Observatory for Human Rights (SOHR) confirmed that Palmyra had fallen to ISIS on Sunday after Syrian armed forces pulled out from the desert city, the organization said.
"Despite the ongoing air raids, IS retook all of Palmyra after the Syrian army withdrew south of the city," said Observatory head Rami Abdel Rahman, using another acronym for the group.
ISIS' own media wing, the Amaq news agency, also reported that the jihadist group's forces had regained "full control" of the city.
ISIS first seized control of Palmyra, a UNESCO World Heritage Site, in May 2015. Syrian government forces recaptured it in March this year.
But on Saturday, ISIS had made new inroads in the city, taking neighborhoods and key sites as Syrian troops focused on a ground operation in the city of Aleppo, SOHR said.
Sana added that the jihadist group had transported troops in from Raqqa, its de facto capital in northern Syria, and the city of Deir Ezzor in the country's east.
ISIS fighters had seized almost the entire city Saturday before Russian warplanes began an intense bombardment, forcing the militants to withdraw to orchards and towns on Palmyra's