Russia launched a strike on the southern Ukrainian city of Odesa on Wednesday while President Volodymyr Zelensky and Prime Minister Kyriakos Mitsotakis of Greece were visiting.

Neither was hurt, and they continued their visit of the strategic port city. It is unclear whether the Russian Army specifically targeted them, or how close they were to the explosion.

Mr. Mitsotakis said at a news conference in Odesa that he and Mr. Zelensky were visiting the city’s port at the time of the assault. “We heard the sound of sirens and explosions that were very close to us,” he said. “We didn’t have time to go to a shelter.”

Dmytro Pletenchuk, a spokesman for the Ukrainian Navy, said that Russia had struck port infrastructure in the city and that five people had been killed.

“You see who we are dealing with,” Mr. Zelensky said. “They don’t care where they strike, whether they are military, civilians, international guests — it doesn’t matter to these people.”

Oleksiy Goncharenko, a Ukrainian lawmaker who was in Odesa at the time of the attack, said it occurred around 10:40 a.m. “I heard explosions, I was very close to the port,” he said in a text message. “It was very loud.”

It was not immediately clear what weapons Russia used, but Ukraine’s Air Force reported the possible deployment of ballistic missiles. Mr. Pletenchuk said an investigation was underway.

Russia said that its army had launched “a high-precision missile strike on a hangar in the industrial port area of Odesa where preparations were being made for the combat use of unmanned boats of the Ukrainian Armed Forces.”

Ukraine has frequently used sea drones to target vessels of Russia’s Black Sea Fleet. On Tuesday, it claimed to have sunk a patrol ship off the coast of Russian-occupied Crimea. “This is the third Russian Black Sea Fleet vessel sunk in the past five weeks,” Britain’s military intelligence said.

Odesa, a lifeline for the Ukrainian economy, is home to a vast port infrastructure vital to Ukraine’s Black Sea exports. Many vessels depart from the port to ship grain and other agricultural products across the Black Sea.

But for the past six months, Russia has been targeting grain silos and naval infrastructure with drones and missiles.

The attacks have also caused civilian casualties, either from direct targeting or falling debris. Last week, a drone hit a residential building, killing 12 civilians. It took rescue workers several days to pull the bodies from the rubble, including those of babies and children.

Mr. Zelensky and Mr. Mitsotakis visited the site of last week’s attack on Wednesday to pay tribute to the victims, laying bouquets of flowers at a makeshift memorial in front of the building. They also visited a cathedral badly damaged by a previous Russian missile strike.

The Ukrainian leader said at the news conference that Wednesday’s attack “speaks to the fact that we need to defend ourselves first and foremost.”