ISTANBUL (AFP) - Ukraine on Wednesday (June 22) played down the chances of reaching a UN-brokered agreement with Russia that could allow blocked grain shipments to start flowing across the Black Sea.

Kyiv's words of caution came after Turkey - a key player in talks aimed at easing growing alarm about global food security - said a deal with Moscow allowed one of its ships to leave a Russian-held port for the first time since the Kremlin's February invasion.

"We welcome the UN Secretary-General's efforts to unblock grain exports from Ukrainian seaports," the Ukrainian foreign ministry's spokesman Oleg Nikolenko said on Twitter.

"Consultations are ongoing. Yet no concrete agreements on holding talks with Ukraine, Russia, Turkey and UN have been reached so far. Security remains a key element of Ukraine's position."

Turkey has been spearheading efforts to resume grain deliveries across the Black Sea that have been stalled by minefields and a Russian military blockade of Ukrainian ports.

The Turkish defence ministry had earlier said that its "constructive" meeting with Russian generals in Moscow resulted in "an understanding for future negotiations between Turkey, Russia, Ukraine and the UN".

"In this context, it was decided that a four-way meeting should be held in Turkey in the coming weeks, after a meeting with the Ukrainian side and the UN," the defence ministry said.

Turkish media said the four-way grain talks could be held in Istanbul next week.

The Turkish defence ministry added that the Moscow meeting allowed its Azov Concord dry cargo vessel to leave a port in Mariupol - a city devastated by a weeks-long siege Ukrainian officials estimate claimed 20,000 lives.

It was not clear from the Turkish statement if the ship was carrying any grain.

Moscow denies blocking the passage of cargo vessels and blames Western sanctions against Russia for contributing to the food crisis.

A Russian defence ministry statement about the Turkish meeting also noted no discernible progress.

"The parties discussed the safe exit of Turkish merchant ships and the export of grain from Ukrainian ports, as well as approaches to ensuring safe navigation in the Black Sea," the Russian statement said.

The grain crisis has seen food prices soar and contributed to the global spike in inflation.

The United Nations warns that it is affecting poorer African countries the most because of their heavy dependence on Russian and Ukrainian wheat.