Here is a recap of relations between the strategically important nations, both heavily involved in the Syrian conflict and with strained ties with the West, since the crisis three years ago.

- Russian jet downed -

On November 24, 2015 a Turkish military jet blasts a Russian warplane out of the sky over the Turkey-Syria border.

Turkey insists the Russian plane -- deployed as part of Moscow's military campaign in support of Syrian President Bashar al-Assad's fight against rebels -- strayed into Turkish airspace.

Moscow adamantly denies the claim and a furious President Vladimir Putin labels the incident a "stab in the back".

- Sanctions -

Moscow fires back by announcing a raft of economic sanctions against Ankara, targeting trade in areas like agriculture, tourism and construction.

A war of words between Putin and President Recep Tayyip Erdogan rages as Moscow demands an apology.

Russia also accuses Erdogan of profiting from the illegal oil trade with Islamic State (IS) jihadists, claims the Turkish leader slams as "slander".

- Reconciliation -

In late June 2016 the Kremlin says Erdogan has apologised for the jet downing in a message to Putin, in which he calls for a return to friendlier ties.

After talking to Erdogan, Putin -- whose own country is battling Western sanctions over Ukraine and low oil prices -- immediately announces an end to the tourism bans and the normalisation of trade ties.

- Coup call -

In a sign that ties are warming, Putin is one of the first international leaders to call Erdogan and offer support after a failed coup against the Turkish president in July 2016.

He does not criticise Erdogan over a subsequent widely condemned purge of thousands perceived to have supported the coup.

- Erdogan heads to Russia -

Putin's hometown of Saint Petersburg in August 2016 hosts the first meeting between the two leaders since the 2015 plane incident, aimed at sealing the rapprochement.

In December Russia's ambassador to Turkey, Andrei Karlov, is shot dead by an off-duty Turkish policeman. Moscow and Ankara say the act is a "provocation" aimed at sabotaging their reconciliation.

- Energy, defence -

In February 2017 Putin gives the green light for the construction of the TurkStream pipeline between Russia and Turkey which will eventually pump gas to the European Union.

Several months later he signs a decree ordering the lifting of most of the remaining sanctions.

In December Russia says it has completed negotiations with Turkey for the sale of an S-400 air defence missile system, with delivery scheduled for late 2019.

- Syria -

Russia and Turkey have also over the past months reinforced cooperation on the question of the dragging Syrian war. This is even though Russia is one of the main allies of Assad while Turkey backs the rebels trying to unseat him.

With Assad-backer Iran they launch in early 2017 peace talks in Astana, Kazakhstan, becoming the powerbrokers in Syria and sidelining the United States.

In January 2018 Turkey launches an operation inside Syria against the Kurdish People's Protection Units (YPG) militia, which it considers a "terrorist" group despite its work with Washington against IS.

The leaders of Turkey, Russia and Iran meet in Ankara on Wednesday to coordinate policy on the war in Syria.

- Spy poisoning -

In March Britain blames Russia for the poisoning on its soil of former Russian double agent Sergei Skripal and his daughter in Salisbury. As a raft of countries join together to punish Moscow, Erdogan says Ankara will not take similar measures and that the charge is "based on allegation".