A Ukrainian official said early Wednesday that a Russian missile attack overnight had killed three people and injured three others in Odesa, a southern Ukrainian city that has been a regular target of Russian missiles and drones trying to destroy its port infrastructure.

The attack followed a Russian airstrike on Monday evening that killed five people and wounded about 30 others, Ukrainian officials said.

Videos and photos from the Monday strike showed lifeless and bloodied bodies of civilians lying on a seafront promenade not known to be close to any strategic site like military buildings or grain storehouses.

The Ukrainian authorities on Tuesday accused Russia of using cluster munitions — a controversial and widely banned weapon that can often cause indiscriminate harm to civilians — in that attack.

The assault early Wednesday also damaged civilian infrastructure in Odesa, Oleh Kiper, the head of the military administration in the region, said on the Telegram messaging app.

Andriy Kostin, Ukraine’s prosecutor general, said in a statement that Russia had fired an Iskander ballistic missile with a cluster warhead in the Monday assault. “The investigators have a reason to believe that the decision to use such a weapon was taken by the Russian military officers deliberately to kill as many Ukrainian civilians as possible,” Mr. Kostin said.

His claim could not be independently verified. The statement included a video of the attack, which showed that the assault targeted a port area with several sports facilities nearby. The video also shows a constellation of some 30 explosions in quick succession across the port neighborhood. The New York Times verified the authenticity of the video but not the nature of the weapon used.

Minutes before the explosions, Ukraine sent a warning via a Telegram channel of a missile launch from Crimea headed toward Odesa.

Konrad Muzyka, a military analyst with Rochan Consulting in Poland, said the explosions appeared to be the result of a cluster munition. Bridget Brink, the United States ambassador to Ukraine, wrote on the social media site X that Russia had used cluster munitions in that attack, adding, “The brutal and relentless nature of Russia’s war cannot be overstated as these attacks on civilians are continuing every day.”

There was no comment from the Kremlin on the strikes in Odesa. American officials said they were aware of the Monday attack and of the Ukrainian claims of cluster munitions, but could not confirm the use of the munitions.

Because of the danger of cluster munitions to civilians, more than 100 countries have signed a 2008 treaty known as the Convention on Cluster Munitions, promising not to make, use, transfer or stockpile them. The United States, Russia and Ukraine are not parties to the treaty.

Both Russia and Ukraine have used cluster munitions — a class of weapon comprising rockets, bombs, mortars, artillery shells and missiles that split open midair and disperse smaller submunitions like explosive bomblets, over hundreds of square feet — in the war.

Originally designed before the advent of guided weapons, they are typically inaccurate weapons designed to attack targets like air defense sites, armored vehicles and dismounted troops in a general area, and have often been used on the front lines.

Bomb disposal experts and human rights groups have said those bomblets, which are mass-produced and inexpensively made, generally have a 20 percent failure rate, often leaving behind hazardous duds that can explode later if mishandled. Because they are small, those duds can lay unnoticed among debris or vegetation and weigh so little that children can pick them up without realizing their danger.

If confirmed, their use in Monday’s attack could mark an escalation in Russia’s tactics that are intended to make life miserable for Ukrainian civilians, including bombing power plants to cut off electricity to major cities. Moscow has repeatedly targeted urban centers in recent weeks, sometimes using weapons usually reserved for combat zones.

The area targeted in Monday’s attack is popular with locals, who often take walks there. A nearby Gothic-style building known locally as the “Harry Potter Castle,” which houses a private law academy, was engulfed in flames after the attack.

“The Russians fired a ballistic missile with a cluster munition at one of the most popular locations among Odesa residents and visitors, where people were walking their children, dogs, playing sports,” Mr. Kiper said on social networks.

Mr. Kiper said a dog had also been killed in the attack. Unverified pictures from the attack’s aftermath showed a woman in sportswear kneeling over a bloodied white dog, as well as a woman lying at the foot of a bench next to a pavement with marks of impact.

Mr. Kostin, the prosecutor general, said that fragments of the weapon had been found within a radius of 1.5 kilometers, or about a mile, from the site of the impact.

The United States agreed last year to send the Ukrainian army 155-millimeter cluster munition artillery shells to help it press ahead with its summer counteroffensive. The decision drew criticism from human rights organizations that pointed to the indiscriminate harm the weapons can cause civilians.

Ukrainian officials and military experts say that Russia’s intensified attacks against big cities in recent weeks are intended to intimidate residents and create panic.

A prime target has been Kharkiv, Ukraine’s second-largest city, just 25 miles from the Russian border. Since March, Russia has been targeting it for the first time with one of the deadliest weapons in its arsenal: powerful guided weapons known as glide bombs, which are dropped from warplanes and deliver hundreds of pounds of explosives in a single blast. The bombs are difficult to shoot down with air defense systems, leaving people essentially helpless.

On Tuesday, Russia again targeted Kharkiv with three glide bombs according to a statement from the Kharkiv regional prosecutor’s office. The strike killed at least one person and injured at least eight others, the prosecutor’s office said.

Dr. Oleksandr Volkov, a Kharkiv-based medical doctor with the International Rescue Committee, a humanitarian organization, said in an email statement that the recent spate of strikes has made living conditions in the city “increasingly uncomfortable, marking a significant deterioration compared to just six months ago.”

Eric Schmitt contributed reporting from Washington, D.C.