Fighters from the so-called Islamic State group have been forced from the centre of the Syrian city of Palmyra, hours after they tried to retake it.
Russian air strikes forced the militants to retreat to the outskirts, Russia and local activists say.
The Syrian army also sent reinforcements to the city, reportedly diverting troops from Aleppo.
IS held the Unesco World Heritage site of Palmyra from May 2015 until they were forced out in March this year.
The group launched its offensive earlier in the week. Its fighters re-entered Palmyra on Saturday, when a local activist said that the city had fallen “more or less” into IS hands.
Now the UK-based Syrian Observatory for Human Rights says “intense” bombing from Russian planes forced IS to withdraw to the orchards on the city’s outskirts.
Fighting continues in those areas.
Moscow said the Syrian army had repelled IS with air support from its forces. The Russian Defense Ministry said it had carried out 64 strikes during the operation, and claimed to have killed more than 300 militants.
A report said IS militants had driven cars filled with explosives during the battle. Palmyra is seen as strategic for IS because it lies close to oil fields.
IS destroyed a number of monuments and beheaded the archaeological director during its 10-month occupation of the site and the adjacent city of Tadmur.
Two 2,000-year-old temples, an arch and funerary towers were left in ruins.
The jihadist group, which has also demolished several pre-Islamic sites in neighboring Iraq, believes that such structures are idolatrous.
The latest battled in Palmyra happened as the Syrian army closed in on the remaining rebel-held area of the city of Aleppo.
Rebel forces said that they had halted the advance of government forces in the pockets they still control in Aleppo.
One rebel commander said a reason for the slowed government advance could be the redeployment of troops to Palmyra.
However, the Syrian government has been continuously advancing on the rebel areas, backed by Russian air support, and now reportedly controls 93% of the city.
US Secretary of State John Kerry called on the Syrian government and the Russian military to “show a little grace” as they mopped up the remaining rebel-held areas of Aleppo.
He was speaking after a meeting in Paris of governments that back the Syrian opposition.
U.S and Russian officials are due to meet in Geneva to discuss the possible evacuation of civilians and rebel fighters from Aleppo.