The European Union (EU) foreign policy chief Josep Borrell has visited the embattled Ukrainian port city of Odesa on the Black Sea, where he saw first hand the damage inflicted by Russian attacks.

Odesa's old quarter and the historic Orthodox Cathedral of the Transfiguration near the port were badly damaged by a Russian bombardment in July. Harbor infrastructure that is key to Ukraine's grain exports has also been hit recently.

As he toured the cathedral site, Borrell called the Russian assault on the city "barbaric." "This is a good example of how Russia is trying to destroy Ukraine," Borrell said, pointing to the ruins behind him in a video released by his agency.

He lamented that it had been one year since Moscow illegally annexed four regions in the south and east of Ukraine. He promised that Europe would not abandon Ukraine in its grinding war to recapture those areas, saying further military, economic, political and diplomatic support was needed.

Borrell again reproached President Vladimir Putin for ending the UN-brokered agreement that allowed Ukrainian grain exports across the Black Sea, despite Russia's blockade of the ports. The deal is seen as essential to addressing global food insecurity and containing grain prices. Borrell noted that Ukraine had once been the largest supplier of grain to the UN's World Food Programme.

Borrell's trip was not announced in advance for security reasons. No details were given on what else was on his agenda. Almost two weeks ago, the Spanish diplomat said that he would soon organize a meeting of the foreign ministers of the 27 EU member states in Kyiv.