Russia isn't conducting operations in Syria involving its own ground troops and won't do so, Admiral Vladimir Komoyedov, the head of the lower house of parliament's defence committee, says, amid confusion over whether "volunteers" may be getting involved.

Komoyedov, who on Monday had said it was likely that Russian volunteers would travel to Syria to fight, was also quoted as saying that Russia was blocking any attempts by its citizens to fight on either side in the Syrian conflict.

The New York Times reported Tuesday that Russian "volunteers" would join the fight in Syria and that a Russian ground force "could fundamentally alter the conflict."

In this photo taken from Russian Defence Ministry website footage Tuesday, two Russian SU-25 ground attack aircraft take off from an airbase Hmeimim in Syria. (Associated Press)

The use of volunteers seemed similar to Russia's "stealth tactic" in using soldiers to seize Crimea from Ukraine in March 2014 and aiding rebels in eastern Ukraine, the Times said.

The paper also reported that U.S. military officials believe there are already more than 600 Russian military personnel in Syria.

Russian Foreign Ministry spokeswoman Maria Zakharova repeated Tuesday that Russia has no plans to carry out ground operation in Syria, and volunteers will not be encouraged by Russian officials to take part in the war.

Russian jets hit Islamic State targets in the Syrian city of Palmyra and the northern province of Aleppo, Syrian state television said on Tuesday, quoting a military source.

In this photo taken from Russian Defense Ministry official website footage on Monday, a bomb is released from Russian Su-24M jet fighter in Syria. (Associated Press)

The strikes destroyed 20 vehicles and three weapons depots in Islamic State-held Palmyra, it said. In Aleppo, they hit the towns of Al-Bab and Deir Hafer, about 20 kilometres east of a military airport currently besieged by Islamic State fighters.

Al-Manar television, run by the Lebanese Hezbollah group which is allied to President Bashar al-Assad, said the Russian air force also carried out four raids in the Jabal al-Zawiya area in the northwestern province of Idlib.

Roman-era ruins

Islamic State forces captured Palmyra in May, an advance which brought them closer to the core of government-held territory in western Syria. It also put the city's Roman-era ruins under the militants' control.

Syria's antiquities chief Maamoun Abdulkarim said on Sunday Islamic State fighters blew up Palmyra's Arch of Triumph, one of the most treasured monuments in the 2,000-year-old city. They had already destroyed temples and other antiquities.

Russian Foreign Ministry spokeswoman Maria Zakharova speaks during a special news briefing in Moscow Tuesday. (Maxim Shipenkov/EPA)

Russia has carried out dozens of strikes in Syria since launching its air campaign last Wednesday.

While Moscow says its intervention targets the hardline Islamic State fighters who control much of eastern and northern Syria, many of the Russian strikes so far have hit rival insurgent forces opposed to Assad.