Russian jets are flying up to 25 bombing raids daily to back up a Syrian government offensive to recapture the ancient city of Palmyra from Islamic State jihadists, the armed forces said Friday.
Senior commander Sergei Rudskoi insisted that the "conditions have been created for the encirclement and definitive defeat of IS armed formations in Palmyra".
"Government troops and patriotic forces with the support of the Russian air force are carrying out a large-scale operation to liberate Palmyra," he told journalists.
"On average Russian planes are flying 20 to 25 combat sorties each day," Rudskoi said.
Russian President Vladimir Putin on Thursday spoke of "intense battles" going on around Palmyra as he decorated Russian officers who served in Syria and said he hoped the "pearl of world civilisation" would be returned to the Syrian people.
The ongoing strikes come despite some of Moscow's jets in Syria returning home after Putin -- one of the main backers of Syrian President Bashar al-Assad -- on Monday ordered a surprise withdrawal of most of his forces from the war-torn country.
The IS jihadist group has claimed the killing of five Russian troops in fighting near Palmyra.
"The soldiers of the caliphate, by the grace of God, have killed five Russian soldiers and six members" of the Syrian army, IS said in a statement.
The group also claimed the killing of several members of the Lebanese Shiite Hezbollah group in the clashes near Palmyra.
A website linked to IS, Aamaq, carried a similar claim and a video showing the bloodied corpse of a man in military gear that it claimed was a Russian military advisor.
The footage also shows equipment presumably captured after the clashes, including a customised AK-74M rifle, a helmet and a compass.
Kremlin spokesman Dmitry Peskov did not confirm either the presence of Russian advisors around Palmyra or the IS claim of the soldiers' killing.
"The advance (on Palmyra) is carried out by contingents of the Syrian army," Peskov said.
IS seized Palmyra, a UNESCO World Heritage Site in eastern Syria known as the "Pearl of the Desert", last May, drawing global concern.