Ukraine dispatched an explosive mounted on a drone that hit the headquarters of Russia’s Black Sea Fleet Sunday. Officials say at least five people were injured in the attack in Russian-held Sevastopol.

Sunday is Russia’s Navy Day. Russian President Vladimir Putin marked the day by attending the annual Navy Day parade in St. Petersburg with an announcement that the Russian Navy is set to receive what he described as “formidable” hypersonic Zircon cruise missiles in the next few months.

Hypersonic weapons fly at speeds of at least Mach 5 and are highly maneuverable and able to change course during flight. They are different from ballistic missiles, which can also travel at hypersonic speeds of at least Mach 5 but have set trajectories and limited maneuverability.

The ability to launch highly maneuverable weapons at hypersonic speeds gives any country a considerable advantage, because such weapons can evade just about any defense system currently in use.

“It doesn’t matter what the threat is. If you can’t see it, you can’t defend against it,” General John Hyten, the former vice chairman of the U.S. Joint Chiefs of Staff, told an audience in Washington in January 2020.

Ukrainian President Volodymyr Zelenskyy called Saturday for the evacuation of eastern Donetsk province, the region that has seen the fiercest fighting as Russia seeks to fully control it.

Hundreds of thousands of people, including children and the elderly, remain in combat zones of the larger Donbas region, which includes Donetsk and Luhansk. It is also the region where Ukrainian prisoners of war died in a missile attack earlier this week.

Zelenskyy made the announcement Saturday during his nightly video address to his nation.

“The more people leave [the] Donetsk region now, the fewer people the Russian army will have time to kill,” he said, adding that residents who left would be given compensation, he said according to Reuters.

Zelenskyy promised logistical support to persuade people to leave.

“Many refuse to leave but it still needs to be done,” the president said. “If you have the opportunity, please talk to those who still remain in the combat zones in Donbas. Please convince them that it is necessary to leave.”

Earlier Saturday, Ukraine demanded that Russia be held accountable for a missile attack that killed dozens of Ukrainian prisoners of war at a Russian-operated detention facility in eastern Ukraine.

The Ukrainian government on Saturday called on the United Nations and the International Committee of the Red Cross to immediately investigate Friday’s attack. The ICRC said Saturday that it still had not been granted access to the site.

With international outrage building over the missile strike, the United Nations pledged support to help investigate the prison attack.

“In relation to the recent tragedy at the prison in Olenivka, we stand ready to send a group of experts able to conduct an investigation, requiring the consent of the parties,” said Farhan Haq, deputy spokesperson for the U.N. secretary-general in a statement released Saturday.

Russia and Ukraine have accused each other of carrying out the attack. Neither claim could be independently verified. So far, no international aid organizations have been granted access to the bombed-out site.

In a statement Sunday, Russia said it has invited United Nations and Red Cross experts to investigate the deaths at the prison, according to Reuters.

The statement from the Defense Ministry said it was acting “in the interests of conducting an objective investigation” into what it called an attack on the prison earlier in the week.

Russia insisted Ukraine used American-made weapons to hit the prison to prevent its own fighters from surrendering to Russian forces.

Ukraine’s armed forces disputed the claim and said Russian artillery targeted the prison camp to hide the mistreatment of the prisoners.

Zelenskyy called the attack a deliberate Russian war crime and a mass murder of Ukrainian prisoners of war.

The Ukrainian army is trying to get the bodies of those killed returned, but Russia has only released the names of the dead.

Meanwhile, fighting raged on as Ukraine’s military claimed its forces killed more than 100 Russian soldiers in the southern area of Kherson. Military officials Saturday said its forces bombed railway and road bridges inside Russian-controlled territories.

Russia announced Saturday its forces killed more than 130 elite Ukrainian soldiers aboard a train in the Donbas region last week and were making gains in other locations on the battlefield.

Grain shipments

In other developments, the first ship loaded with Ukrainian grain is set to sail from the Black Sea port of Chornomorsk, perhaps as early as Monday.

Last week Russia and Ukraine agreed to unblock grain exports from Black Sea ports, which have been threatened by Russian attacks since the invasion. The blockade of grain in Ukraine, one of the world’s biggest exporters, has led to sharp increases in global food prices.

Grain shipments from the country were to resume after a U.N. brokered agreement was signed in Turkey last week.

On Friday, U.S. Secretary of State Antony Blinken spoke by phone with Russian Foreign Minister Sergey Lavrov and mentioned the importance of Russia following through on the agreement.

Blinken also warned of consequences should Moscow move ahead with suspected plans to annex portions of eastern and southern Ukraine.

Some information for this report came from The Associated Press and Reuters.