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

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.

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 Mr Erdogan.

Moscow rejected Turkey's assertion that its SU-24 fighter jet had flown into Turkish air space for 17 seconds after ignoring repeated warnings to change course.

A senior Russian commander said the jet had in fact been "ambushed" by two Turkish F-16s patrolling the area for more than an hour beforehand.

He said Russian and Syrian radar data proved that a Turkish jet had fired a missile from 2km (1.2 miles) inside Syria. Turkey did not respond to the allegation.

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 30 September.

Turkey, which is a member of Nato and of a US-led coalition in the region, insists Mr Assad 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.