But the militants launched a fresh attack on Sunday, the Observatory said, recapturing all of Palmyra after government forces pulled out.
State news agency SANA quoting an unnamed military official saying that the militant group received reinforcements from its de-facto capital in Raqqa, enabling it to attack with "large numbers" against military checkpoints around the city.
A statement by IS's news agency Amaq said the group had taken the strategic Jabal al Tar and Jabal Antara mountains that overlook Palmyra in some of the heaviest fighting since IS lost the city. Thousands of civilians poured out of rebel areas of Aleppo as Syria's army pushed to take the last remnants of opposition-held territory in the devastated city.
"Seizing on the suspension of active military action near Al-Raqqah till spring by the USA and global coalition, Islamic State devoted considerable forces to storm Palmyra", Konashenkov asserted. A map distributed by the Observatory shows the IS-controlled areas extend east, south and north of Palmyra. Jay also noted that Islamic State (IS, formerly ISIS/ISIL) might use the attack on Palmyra [listed as UNESCO heritage] as a PR tool since "the world cares a great deal [more] about Palmyra than it probably does about Aleppo, and ISIS knows this". In Palmyra, that had meant ceding control largely to the Syrian army. The few remaining families also are trying to leave, he said. According to AP, citing the activist-run Palmyra Coordination network, militants gained footholds in the northern and northwestern districts of Palmyra.
Russia's Defense Ministry said its jets had delivered 64 airstrikes overnight and claimed to have killed 300 militants in the raid. IS seized the town previous year and held it for 10 months before being driven out by Russian-backed Syrian forces in March.
After a sudden regime withdrawal, IS militants made a lightning-fast advance across Palmyra, sparking new concerns for its remaining ancient treasures. During that time it dynamited a number of temples and destroyed other artifacts.
In the previous year, IS has suffered defeats in both Syria and Iraq, losing several towns and cities it had captured in 2014.
An Islamic State recapture of Palmyra would be a major reversal for Syria's government and its Russian backer which hailed the city's capture in March, sent troops to protect it and even staged a concert there. After tightening the siege on the eastern part of Aleppo city, the most prized urban stronghold for the opposition, government and allied troops have been steadily carving into the besieged enclave in a ground offensive that began late November.