DAMASCUS, Dec. 10 (Xinhua) -- The Islamic State (IS) group has retreated from points it reached in the ancient city of Palmyra in central Syria as a result of intense airstrikes by Russia and Syria on Saturday, pan-Arab al-Mayadeen TV reported.

The airstrikes targeted several areas near Palmyra in a bid to push back IS, which attempted to attack the city and has reportedly re-entered it after losing it to the Syrian government forces in nine months ago.

Meanwhile, a military source told Xinhua that the Syrian forces have thwarted an infiltration attempt by IS to enter the eastern part of Palmyra.

Earlier, the Syrian Observatory for Human Rights said the IS entered that oasis city on Saturday.

"The IS is in the city of Palmyra for the first time after losing it to the Syrian army, whose forces are collapsing in the city," said the Observatory.

The UK-based watchdog group said the IS group succeeded to advance and reach the vicinity of the Palmyra hospital in the northwestern outskirts of the city, after capturing the Amiriyeh suburb in the northern part.

The IS militants also captured the Tar mountain, close to the Palmyra Citadel, west of the city, in tandem with shelling the citadel with mortar shells and heavy artillery.

The Observatory said intense battles were still raging between the IS militants and the Syrian government forces in the city.

The IS started its offensive on Palmyra on Thursday, after bringing in hundreds of fighters for taking the city, according to the Observatory.

The Syrian army are fighting to restore the positions it had lost in Palmyra as a result of the IS attack, the Observatory said.

The Syrian army captured Palmyra on March 27, 2016, a year after losing the city to the IS.

Palmyra contains the monumental ruins of a great city that was one of the most important cultural centers of the ancient world.

The city has an importance to IS as it connects areas under the terror group's control in the eastern province of Deir al-Zour with areas under its control in the eastern countryside of the central province of Homs.

The recapture of Palmyra is also important as the group's fighters in Iraq have started entering Syria recently after suffering great losses in battles against the Iraqi army and the U.S.-anti-terror coalition.