The missiles, launched from a Russian flotilla in the Caspian Sea, travelled 1,400km over “unpopulated areas” to target militants, according to a Russian officer.
The latest developments, exactly a week after Russia began launching air strikes in Syria, add a new layer to the fray in the complex war that has torn the Middle East country apart since 2011.
Moscow has mainly targeted central and north-western Syria, strategic regions that are the gateway to president Bashar Assad’s strongholds in Damascus, and along the Mediterranean coast.
But the strikes appear to have given Assad new confidence to try to retake some lost ground.
According to the Syrian official, the government push is concentrated in the adjacent provinces of Hama and Idlib where rebels have been advancing in past months.
IS is not present in the areas where the fighting is under way.
The offensive in central Syria and the ensuing clashes with militants, including al Qaeda’s Syrian branch, was the first major ground fighting since Moscow began launching air raids in Syria last week.
The Russian air strikes appear to have emboldened Syrian troops to launch the ground push after suffering a string of setbacks in north-western Syria over the past few months.
In Moscow, Russian defence minister Sergei Shoigu said Russia is using warships in the Caspian Sea to target IS in Syria.
Mr Shoigu told president Vladimir Putin in televised remarks that Russia yesterday carried out 26 missile strikes from four warships of its Caspian Sea flotilla.
Mr Shoigu said the operation destroyed all the targets and did not launch any strikes upon civilian areas.
Andrei Kartapolov, of the Russian General Staff, told Russian newsagencies that Russia had planned the missile strikes from the warships so that they would be flying “over-unpopulated areas”.
Mr Shoigu also said Russia has carried out 112 air strikes on IS positions since its operation began on September 30. The Britain-based Syrian Observatory for Human Rights said a government offensive began on four fronts yesterday in the north-western provinces of Idlib and neighbouring Hama.
Observatory director Rami Abdurrahman described it as “the most intense fighting in months.” In Syria, the leader of a US-backed rebel group, Tajammu Alezzah confirmed the ground offensive, claiming there were Russian and Iranian soldiers in the operation.
The rebel group’s commander, Major Jamil al-Saleh, said the offensive, accompanied by air cover and shelling, came from three fronts, including Latamneh, north of the Hama province where his group is based, and Kfar Zeita to the north.
The offensive targets the rural part of northern Hama and Idlib, the north-western province, almost totally controlled by rebel groups, he said.
Activist Ahmad al-Ahmad, who is in Idlib, said government troops are “heavily” shelling central areas after rebels attacked an army post and destroyed a tank there.
The observatory, which has a network of activists on the ground, and al-Ahmad said the main launching point for government forces is the town of Morek on the highway that links the capital, Damascus, with the northern city of Aleppo, Syria’s largest city and former commercial centre. Rebels have controlled areas on the highway since 2012.
The Local Co-ordination Committees, another activist group, said rebels were able to destroy two tanks and an armoured personnel carrier in northern parts of Hama province near Idlib.
The observatory said 37 Russian air raids areas hit the area of fighting yesterday alone.
The observatory said two helicopters believed to be Russian were seen flying at low altitude in Morek.
It said militants opened fire at the helicopters without striking them. It was not immediately clear if the pilots were Russian or Syrian.
The Syrian military has Russian-made helicopters in its airforce.