Russia has strengthened its anti-aircraft defences in Syria by moving a cruiser towards the coast and deploying new missiles at its main base, BBC News reports.

The Moskva cruiser's long-range air defence system will provide cover for Russian aircraft, as will the S-400 missiles which arrived on Thursday, November 27.

The row over Turkey's downing of a Russian combat jet on Tuesday rages on.

Turkish President Recep Tayyip Erdogan has warned Russia not to "play with fire" with its operations in Syria.

Russia has suspended its visa-free arrangement with Turkey and is planning to introduce a wide range of economic sanctions. President Vladimir Putin wants an apology from Turkey before he will speak to Erdogan.

The long-range S-400 system was delivered to Russia's Hmeimim air base just 50km from the border with Turkey.

Russian aircraft have been using the base to attack opponents of Syrian President Bashar al-Assad since September 30.

Turkey, which is a member of Nato and of a U.S.-led coalition in the region, insistsAssad must step down before any political solution to the Syrian conflict is found.

Both countries say they are trying to rid the region of the so-called Islamic State (IS) group, which claimed the recent attacks on Paris and also on a Russian airliner.