Cargo ships loaded with grain and other agricultural products left Ukrainian ports on Monday despite Russia's decision to pull out from a landmark deal designed to ease a global food crisis.
As one of the brokers of the grain deal, Turkey has stepped up diplomacy with the two warring countries in a bid to save it as Russia warned that continuing to enforce the agreement without its participation would be "dangerous".
"Civilian cargo ships can never be a military target or held hostage. The food must flow," Amir M. Abdulla, the UN Coordinator for the Black Sea Grain Initiative, tweeted on Monday.
In all, 12 ships were due to leave Ukrainian ports on Monday and four more were due to head to the country, according to the Joint Coordination Center (JCC) that has been overseeing the agreement brokered by Turkey and the UN.
The marine traffic came two days after Russia notified the UN and Turkey that it was suspending its participation in the grain agreement, after Moscow accused Ukraine of a "massive" drone attack on its Black Sea Fleet in Crimea.
Ukraine has labelled the Russian charges as a "false pretext".
Grain prices were up on Monday morning after the Russian decision.
Turkish President Recep Tayyip Erdogan, whose country has stayed neutral throughout the eight-month war in Ukraine, vowed to pursue efforts to keep the agreement in force despite Russia's moves.
"Although Russia acts hesitantly... we will resolutely continue our efforts to serve humanity," Erdogan said in a televised address.
Turkey analyst Soner Cagaptay said if Erdogan managed to convince Russian President Vladimir Putin to get back to the table, it would underline Ankara's brand as the country that can talk to both Ukraine and Russia, from a neutral stance.
"If Turkey is able to return Russia back to the deal, Ankara will be able to say to everyone 'Hey, let me stay where I am because you know that it works and it helps you.' It could be quite a significant diplomatic feet for Ankara," he told AFP.
NATO member Turkey, which has good relations with its two Black Sea neighbours, has refrained from joining Western sanctions on Moscow and instead bolstered its trade while supplying Kyiv with combat drones.
Monday's shipping schedule was agreed by the Ukrainian, Turkish and UN delegations, with Russia informed of the movements, the JCC said in a statement late on Sunday.
A source familiar with the matter said: "As a signatory to the agreement, they have been requested to take the necessary measures to ensure the safety of the vessels."
The Kremlin said it would be "dangerous" to enforce the agreement without its involvement.
"In conditions where Russia talks about the impossibility of guaranteeing the safety of navigation in these areas, such a deal is hardly feasible. And it takes on a different character, much more risky, dangerous," Kremlin spokesman Dmitry Peskov told journalists.
Turkey's defence minister Hulusi Akar said he would speak with his Russian counterpart, Sergei Shoigu, on Monday evening.
"This (agreement) should continue. Suspending this initiative will not benefit Russia, Ukraine or anyone else," he said.
Ukraine, one of the world's largest grain exporters, was forced to halt almost all deliveries following Russia's invasion in late February.
The July deal to unlock its grain exports is critical to easing the global food crisis caused by the conflict.
It had already allowed more than 9.5 million tonnes of Ukrainian grain to be exported and was due to be renewed on November 19.
A separate deal signed with Russia allowed the export of Russian food and fertilisers, despite Western sanctions imposed on Moscow. But it was never implemented, to the dismay of Moscow, which has complained about the issue for weeks.