A hangar housing naval drones in the Black Sea port was hit, according to the Russian defence ministry.

Five people were killed in the attack, said a Ukrainian navy spokesperson.

President Zelenskyy was touring the war-ravaged southern city with Greek Prime Minister Kyriakos Mitsotakis.

The attack happened about 500 to 800 metres from where the leaders were, Reuters reported.

In a joint news conference after the strike, Mr Zelenskyy said: "It seems to me that we have not only heard, we have seen this strike today.

"You see who we're dealing with, they don't care where to hit."

Mr Mitsotakis, who was on his first visit to the country since Russia's invasion in February 2022, said that during a tour of the port and Ukraine's humanitarian corridor, the delegation heard sirens and a big explosion as they headed towards their cars.

"I believe that this is for us the most vivid reminder that there is a real war waging here," Mr Mitsotakis said, urging other European leaders to visit Ukraine to get a first-hand sense of the war's impact on civilians.

The Ukrainian air force announced a ballistic missile threat in the region on Wednesday morning but there were no official reports up until the news conference after the leaders' tour.

Mr Zelenskyy has regularly visited cities and military units on the frontline during the war, always in secrecy until after he has left.

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Foreign leaders have also made several trips to Ukraine, and they occasionally have had to take refuge in shelters when air raid sirens sound.

Ukraine's Black Sea port infrastructure has been a constant target for Russian attacks, which have stepped up since mid-July when Moscow quit a UN-brokered deal that allowed safe passage of Ukrainian grain shipments and Kyiv established its own export corridor.

Russia has launched more than 880 attack drones and 170 missiles on Odesa's port infrastructure since, a Ukrainian navy commander said during the tour.

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Greece, a NATO member and traditional ally to Ukraine's bid to join the military alliance and the European Union, has offered military help to the country.

On Wednesday's visit, Mr Mitsotakis confirmed Greece's continued support.

"My presence here reflects the respect of the entire free world for your people and underlines Greece's commitment to remain by your side," he told Mr Zelenskyy.

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The Ukrainian president also stressed the importance of air defence capabilities and said the countries started work on a bilateral security agreement, similar to one Kyiv has already signed with other nations.

Mr Mitsotakis added that Greece would participate in a high-level Ukraine peace conference in Switzerland, which the host country said would take place "by the summer".

The leaders also visited a residential building - the site of Russian drone attack on Saturday that killed 12 people, including five children.