Story highlights ISIS in control of ancient city, state media reports

Militant group in 2015 blew up ancient treasures there

(CNN) 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.

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"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.

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