ISTANBUL - Russia and Turkey on Monday signed an agreement to build a gas pipeline under the Black Sea, as President Vladimir Putin and Turkish counterpart Recep Tayyip Erdogan vowed to intensify relations after a bitter crisis.

Making his first visit to Turkey since the shooting down of a Russian war plane by Turkey led to the worst dispute between Ankara and Moscow since the Cold War, Putin said the two countries could now return to cooperation in all areas.

Only a few months ago, the two post-imperial strongmen were exchanging bitterly personal accusations. But this was already the pair’s third meeting after a June agreement to normalise ties.

“I have full confidence that the normalisation process between Turkey and Russia will swiftly continue,” said Erdogan. Showing that any personal animosity was over, Putin thanked Erdogan for the “attention Mr President has devoted to the development of Turkish-Russian relations”.

The centrepiece of the one-day visit was the signing of an agreement on realising the construction of the planned TurkStream gas pipeline to pump Russian gas through two lines under Turkish waters in the Black Sea towards Europe.

The chief executive of Russian gas giant Gazprom, Alexei Miller, had said ahead of the signing the annual capacity of each line is to be 15.75 billion cubic metres of gas (bcma), making a total capacity of over 30 bcma.

The agreement aims to build the lines by 2019, Miller said, adding the first line of the gas pipeline will be used to transport gas to Turkish consumers and the second to pipe to Europe.

Russia and Turkey remain at odds over the Syria conflict, with Moscow a key backer of the regime of President Bashar al-Assad while his exit from power is Turkey’s key strategic aim. But Turkey, which just months ago was loudly accusing Russia of war crimes in Syria, has been remarkably tight-lipped over the Syrian regime onslaught on rebel-held areas of Aleppo in recent weeks, as ties with Moscow have tentatively improved.

Analysts have long noted an ability on the part of Moscow and Ankara to show pragmatism in times of good relations and push disputes to one side, concentrating on strategic cooperation that includes a goal to reach annual two-way trade of $100 billion (111 billion euros).

In his speech to the World Energy Congress before their bilateral talks, Erdogan complained how a child in Aleppo “only sees bombs dropped by helicopters and planes that target them” but made no mention of Russia or the Assad regime.

Both leaders agreed to work together to ensure aid can reach the conflict-torn Syrian city of Aleppo. They made no mention of their differences on the Syria conflict or of any breakthrough in finding a joint strategy.

Russia will create a permanent naval base in Syria to expand its military footprint in its closest Middle East ally, a government official said on Monday, a week after Moscow said it was considering reopening Soviet-era bases in Vietnam and Cuba.

The move, announced by Russian Deputy Defence Minister Nikolai Pankov, is further evidence Russia is building up its capabilities in Syria despite a partial drawdown in March and another sign it is digging in for the long haul to help prop up President Bashar al-Assad.

"By doing this Russia is not only increasing its military potential in Syria but in the entire Middle East," Senator Igor Morozov, a member of the upper house of parliament's International Affairs Committee, told the RIA news agency.

A Reuters analysis of publicly available tracking data shows Moscow has steadily built up its forces in Syria since a ceasefire collapsed in late September, doubling supply runs by air and sea. 

The base plan, which will involve upgrading and expanding an existing naval facility at the port of Tartus which Moscow leases from Syria, is part of a push to expand or create a new military presence abroad.

The Izvestia newspaper said Moscow was also in talks to open an air base in Egypt, while the state-owned Rossiskaya Gazeta daily noted that Russia has said it wants bases in Venezuela, Nicaragua, the Seychelles and Singapore too.

At odds with Washington over Syria and Ukraine, Russia has engaged in a bout of sabre-rattling in recent weeks, moving S-300 surface-to-air missiles to Tartus, nuclear-capable missiles to its European exclave of Kaliningrad, and reinforcing its Syria strike force.

The Russian Defence Ministry said on Monday that Russian paratroopers would for the first time also take part in war games with Egyptian paratroopers on Egyptian soil this month.

Pankov said plans for the permanent naval base at Tartus were well advanced. "The necessary papers are ready and are in the process of being approved by different agencies," he told senators. "We hope we can ask you to ratify these documents soon."

Moscow already has a permanent air base in Syria from which it flies air strikes against anti-Assad rebels and uses military trainers, special forces, marines and artillery specialists to help support Syrian government forces on the ground.

Senator Morozov said that having a permanent naval base as well would allow Russia to operate more ships in the Mediterranean as they would have an enhanced facility where they could refuel and resupply.

Moscow inherited the Tartus facility when the Soviet Union collapsed in 1991 and it is now the Russian navy's sole foothold in the Mediterranean. Despite some modernisation, it is currently fairly modest and unable to welcome larger warships.

Leonid Slutsky, a senior parliamentarian, told RIA its capacity would be expanded and it would be equipped with anti-submarine defences and new electronics systems on top of the S-300 missiles it recently received.