Russians warships in the Mediterranean Sea have fired four cruise missiles at the Islamic State group's positions in Syria, the defence ministry in Moscow said.
The announcement came as Syrian government troops pushed ahead in their offensive against IS and militants in central and northern Syria.
Moscow said in a statement that the Admiral Essen frigate and the Krasnodar submarine launched the missiles at IS targets in the area of the ancient town of Palmyra. There was no information on when the missiles were launched.
Syrian troops have been on the offensive for weeks in northern, central and southern parts of the country against IS and US-backed rebels under the cover of Russian air strikes, gaining an area almost half the size of neighbouring Lebanon.
Most recently, Syrian troops and their allies have been marching towards the IS stronghold of Sukhna, about 35 miles north east of Palmyra.
The strategic juncture in the Syrian desert aids government plans to go after IS in Deir el-Zour, one of the militants' last major strongholds in Syria.
The oil-rich province straddles the border with Iraq and is the extremist group's last gateway to the outside world.
Russia, a staunch Damascus ally, has been providing air cover to President Bashar Assad's offensive against IS and other insurgents since 2015.
Moscow had fired cruise missiles from warships in the past, as well as from mainland Russia, against Assad's opponents.
As the fighting against IS militants is under way near Palmyra, Syrian troops clashed with US-backed rebels in the country's south on Wednesday, according to the Britain-based Syrian Observatory for Human Rights and Mozahem al-Salloum, of the activist-run Hammurabi Justice News network which tracks developments in eastern Syria.
The fighting came days after the US told Syrian government forces and their allies to move away from an area near the Jordanian border where the coalition is training allied rebels.
The warning came less than two weeks after the Americans bombed Iranian-backed troops there after they failed to heed similar warnings.
Navy Captain Jeff Davis, a Pentagon spokesman, said on Tuesday that the US dropped leaflets over the weekend telling the forces to leave the protected zone.
Syrian troops backed by Russian air strikes captured Palmyra in March last year and Moscow even flew in one of its best classical musicians to play a triumphant concert at Palmyra's ancient theatre. IS forces, however, recaptured Palmyra eight months later, before Syrian government troops drove them out again in March this year.