Russia and Turkey have signed a $20bn project for Moscow to build and own a controlling stake in Ankara's first nuclear power plant, as the two Cold War-era rivals try to cement a strategic partnership.
Several agreements, including removing visa restrictions and shipping oil products from the Black Sea, were struck during the landmark visit by Dmitry Medvedev, the Russian president, to Turkey.
Sergei Kiriyenko, Russia's nuclear agency chief, said state-controlled building group Atomstroiexport will lead construction of the plant on Turkey's southern coast.
"It's an extremely important contract for us," he said on Wednesday.
Moscow has built nuclear power plants in nations from China to Iran and might build a power plant in Syria, as it aggressively seeks deals to build new stations and boost its presence in foreign energy markets.
Turkey is keen to reduce its dependence on imported energy and cover a looming power shortfall.
Moscow provides 60 per cent of Turkey's gas needs, which has raised concerns that Ankara is becoming too dependent on Russia, a major trading partner.
Such deals would have been inconceivable two decades ago, when Turkey guarded Nato's eastern borders during the Cold War.
"We share a determination to increase the trade volume from a current $38bn to $100bn in five years," Abdullah Gul, the Turkish president, said after hosting talks with Medvedev.
Among the accords signed was one on transporting crude oil from the Black Sea via the Samsun-Ceyhan pipeline.
Transneft, the Russian state pipeline monopoly, said last year that Russian interests may take up to a 50 per cent stake in Turkey's the $3bn pipeline project in exchange for providing much-needed throughput.
The project, co-led by Italy's ENI, will link the Black Sea and the Mediterranean and advance Ankara's plan to turn its southern port of Ceyhan into a regional energy hub.
During his visit, Medvedev said he hoped Turkey and Armenia could restore full relations to help stabilise the volatile South Caucasus region.
A US and Russian-backed peace initiative to end a century of hostility between Armenia and Turkey collapsed last month.
"I hope that in the end the sides can reach all of the necessary agreements and fully restore ties which would without doubt help to stabilise the situation in our region," he said.
Armenia accuses the Ottoman Turks of genocide towards the Armenians during and just after the First World War, but late last year Armenia and Turkey agreed a series of protocols to mend ties.
Medvedev's visit to Turkey followed a trip to Syria, where he called for a more active US role in the Middle East peace process, saying the situation in the region was "very bad" and risked worsening further.
Israel sharply criticised Medvedev on Wednesday for having met Khaled Meshaal, the exiled head of Hamas, in Damascus.
The country's foreign ministry sharply rejected what it said was a call from Medvedev and his Turkish countepart Abdullah Gul to include Hamas in the peace process.
Yigal Palmor, a foreign ministry spokesman, said: "The foreign ministry completely rejects the calls by the Russian and Turkish presidents to include Hamas in the political process, and expresses a deep disappointment from the meeting of the Russian President with Khaled Mashaal in Damascus."