Three ships loaded with grain left Ukrainian ports on Friday under a recently concluded safe passage deal, the Turkish defenсe ministry and Reuters witnesses said.
The first grain ship to set sail from a Ukrainian port since the start of the Russian invasion, departed Odesa on Monday.
"We expect that the security guarantees of our partners from the UN and Turkey will continue to work, and food exports from our ports will become stable and predictable for all market participants," Ukrainian Infrastructure Mnister Oleksandr Kubrakov said on Facebook after the ships set off.
In a rare diplomatic breakthrough in the five-month war, the United Nations and Turkey have brokered a safe passage deal between Moscow and Kyiv, after the United Nations warned of famines due to Ukrainian grain shipments being halted.
Russian President Vladimir Putin sent troops into Ukraine on February 24, sparking the biggest conflict in Europe since World War Two and causing a global energy and food crisis. Ukraine and Russia produce about one third of global wheat and Russia is Europe's main energy supplier.
On Friday, two grain ships set off from Chornomorsk and one from Odesa, with a total of about 58,000 tonnes of corn.
The Turkish Defence Ministry said on Twitter the Panama-flagged Navistar, carrying 33,000 tonnes of corn bound for Ireland, departed from Odesa.
The Maltese-flagged Rojen, carrying 13,000 tonnes of corn, departed from Chornomorsk port bound for Britain. The Turkish-flagged ship Polarnet, carrying 12,000 tonnes of corn, set off from Chornomorsk for the Turkish Black Sea port of Karasu.
The Turkish bulk carrier Osprey S, flying the flag of Liberia, was expected to arrive in Ukraine's Chornomorsk port on Friday, the regional administration of Odesa said. It would be the first ship to arrive at a Ukrainian port during the war.
Ukraine has called for the grain deal to be extended to include other products, such as metals, the Financial Times reported.
"This agreement is about logistics, about the movement of vessels through the Black Sea," Ukraine's Deputy Economy Minister Taras Kachka told the newspaper.
"What's the difference between grain and iron ore?"
After five-months of fighting, Ukrainian President Volodymyr Zelenskiy this week described the pressure his armed forces were under in the eastern Donbas region as "hell".
Moscow is seeking to control the largely Russian-speaking Donbas, comprised of Luhansk and Donetsk provinces, where pro-Moscow separatists gained control of territory after the Kremlin annexed Crimea to the south in 2014.
Zelenskiy spoke of fierce fighting around the town of Avdiivka and the fortified village of Pisky, where Ukraine has acknowledged its Russian foe's "partial success" in recent days.
The Ukrainian military said on Thursday Russian forces had mounted at least two assaults on Pisky but had been repelled.
Ukraine has spent the last eight years fortifying defensive positions in Pisky, seeing it as a buffer zone against Russian-backed forces who control the city of Donetsk about 10 km to the southeast.
Ukrainian General Oleksiy Hromov told a news conference his forces had recaptured two villages around the eastern city of Sloviansk but had been pushed back to the town of Avdiivka after being forced to abandon a coal mine regarded as an important defensive position.
The Russian defence ministry confirmed its offensive.
Reuters could not immediately verify either side's assertions.
The Ukraine war has displaced millions, killed thousands of civilians, and left cities, towns and villages in rubble. Ukraine and its Western allies have accused Russian forces of targeting civilians and war crimes, charges Russia rejects.
On Friday, Ukraine's General Staff said Russian shelling of scores of towns across the country again targeted civilian settlements as well as military infrastructure.