LONDON—Exports of grain are leaving Russia's Azov Sea for Turkey again after suffering delays in the wake of Turkey's shooting-down of a Russian warplane, but some traders remain nervy about striking new deals, according to industry sources.

The continuation of shipments highlights the countries' mutual dependence in international trade. Turkey vies with Egypt to be the largest importer of Russian wheat, while Russia's boycott of some EU products has left it reliant on imports of fruit and vegetables from Turkey.

Gregory Souris, director of Actava Trading DMCC, a Dubai-based brokerage, said Actava finalized customs documents on Thursday for multiple ships waiting to take grain to Turkey from the port of Yeysk on the Azov Sea. The vessels hadn't been granted papers earlier this week, he said, adding that the holdups only applied to ships bound for Turkey.

"It seems to be they are now clearing the vessels," he said.

Erol Yahya, Executive Director of Turkish milling group Intermil-Un, said a 3,000 ton vessel carrying wheat for the company left the Azov Sea Thursday after being delayed in the wake of the destruction of the Russian jet on Tuesday.

Still, the situation remains uncertain with tensions between the countries running high. "It's a mystery to us what's going to happen," said Mr. Souris.

On Thursday, Russia's Agriculture Minister Alexander Tkachyov ordered tighter controls on agricultural products from Turkey, saying some Turkish products don't meet Russian standards.

A Kremlin spokesman said the agriculture ministry's move wasn't an embargo. Russia's introduction of tougher inspections on foodstuffs frequently coincides with heightened tensions with the country affected.

Andrey Sizov, managing director of Russian agriculture consultancy SovEcon, said some Russian trade houses have stopped striking new deals with Turkish buyers, fearing an export ban.

"They are afraid the government will stop these deliveries. If they can't deliver they will have to pay fines," he said.

Still, he said a formal ban is unlikely, given Russia's reliance on Turkish imports. Turkey was the no. 1 destination for Russian wheat, corn, sunflower oil, and sunflower meal in 2014-15, accounting for exports worth around $1.5 billion dollars, according to SovEcon's data.

Turkish millers prize Russian wheat because it is better quality than other Black Sea producing countries, Mr. Yahya said. If it were cut off from Russian supplies, Intermil, whose mill in Ankara can handle around 1,200 metric tons of wheat a day, would have pay $30 to $40 dollars more per ton for grain from Canada, Australia or the U.S., he said.

He pointed out logistical factors that would hinder the two countries if they sought alternative arrangements. The ports of the Azov Sea, where most of Turkey's Russian wheat is handled, can only load small vessels of 3,000 or 5,000 tons. As such, they are well-suited to Turkey's importers, who prefer small shipments because of the higher costs involved when the 60,000-ton vessels used at larger ports encounter delivery problems, he said.

Write to Ed Ballard at ed.ballard@wsj.com

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(END) Dow Jones Newswires

November 26, 2015 19:45 ET (00:45 GMT)