Russian cruise missile attacks
Islamic State positions near Palmyra were treated to several Kalibr cruise missiles launched from a Russian submarine, according to reports.

Via Al Masdar News:
The Russian Navy launched several Kalibr cruise missiles towards the Islamic State's (ISIL) positions in eastern Syria on Sunday, Interfax News Agency reported last night.

According to a statement from the Russian Navy, a submarine off the cast of Syria launched a number of cruise missiles at the Islamic State's positions in eastern Syria.

These Russian cruise missiles reportedly struck the Islamic State's positions in the eastern countryside of Palmyra, where the Syrian Arab Army (SAA) is currently attempting to advance against the terrorist group.

Russia has carried out several cruise missile strikes against the Islamic State in the past; however, they have been less prevalent recently due to the Syrian Arab Army's success on the ground.
But why use cruise missiles? We're sure for a variety of reasons — one being that it's a good way of reminding Washington about Russia's capabilities.

And since Israel is now insisting that it can bomb Syria whenever it wants (with impunity), perhaps a friendly "reminder" is in order.

For an excellent analysis of Russia's strategic use of cruise missiles, we recommend this piece by Daniel Fielding:
Regardless of what happens next, Russia's demonstration of its ability to launch cruise missiles from the Caspian Sea shows why the concerns some have expressed that the US might attack the Russian strike force in Syria are not realistic.

The US has far more air assets in the eastern Mediterranean than do the Russians. However the Russians have now demonstrated that they have the ability to launch cruise missiles from their own territory that can reach US bases in the area.

The US air base at Incirlik in Turkey is especially vulnerable as - probably - are US bases in Bahrain and Saudi Arabia. Any US commander minded to "disarm" the Russian strike force in Syria must now take that capability into account.

That explains why the idea of "disarming" the Russian strike force - if it ever existed - has been abandoned.