Putin will hold an afternoon of talks with his counterpart Recep Tayyip Erdogan before the two strongmen leaders are joined on Wednesday by Iranian President Hassan Rouhani for a summit devoted to Syria.

Putin's visit to Turkey is his first trip abroad since he won a historic fourth presidential mandate in March 18 polls.

Putin and Erdogan -- who have both led their post-imperial states out of economic crisis but also into a new era of confrontation with the West -- have forged an increasingly close alliance in recent months.

Their meeting comes as ties between Russia and the West are nosediving to post-Cold War lows after the March poisoning of Russian ex-double agent Sergei Skripal and his daughter in the UK.

While EU powers have rushed to join Britain in condemning Russia and expelling diplomats over the attack on Skripal, Turkey has been much more circumspect.

Erdogan, who in 2017 held eight face-to-face meetings with Putin, has said that Ankara will not act against Moscow "based on an allegation".

In a move that has troubled Turkey's NATO allies, Ankara has agreed to buy S-400 air defence missile systems from Russia.

But Ankara-Moscow relations were also tested by a severe crisis from November 2015 when Turkey shot down a Russian war plane over Syria, a confrontation both sides are trying to put behind each other.

Despite being on different sides of the Syrian civil war, key regime backers Russia and Iran have joined with rebel-supporting Turkey to boost peace and also influence when the conflict ends.

Cooperation is also flourishing in other areas. Putin and Erdogan will from Ankara via video conference launch construction of Turkey's first nuclear power station in the Mediterranean Mersin region.

The Akkuyu power station -- a project costing over $20 billion (16 billion euros) and heavily disliked by environmentalists -- was already launched once before in February 2015 but then put on hold due to the plane crisis.

Russia and Turkey are also building the TurkStream gas pipeline under the Black Sea that will allow Moscow to pump gas to Europe avoiding Ukraine and increase Turkey's importance as a transit hub.