KYIV, Ukraine — Russia’s Supreme Court on Tuesday declared Ukraine’s Azov Regiment a terrorist organization, a designation that could lead to terror charges against some of the captured fighters who made their last stand inside Mariupol’s shattered steel plant.

Russia and its rebel allies are holding an estimated 1,000 Azov fighters prisoner, many since their surrender at the steelworks in mid-May. Russian authorities have opened criminal cases against them, accusing them of killing civilians. The addition of terrorism charges could mean fewer rights and longer prison sentences.

A terrorist organization’s leaders could receive 15 to 20 years, and group members could get five to 10, according to Russian state media.

In its ruling, the Supreme Court banned the Azov Regiment in Russia. That could also outlaw the regiment in areas of Ukraine occupied by Russian or Russia-backed forces, if those territories go ahead with plans to become part of Russia.

A Ukrainian soldier inside the ruined Azovstal steel plant stands under sunlight in his shelter in Mariupol, Ukraine, on May 7, 2022. Russia’s Supreme Court has declared Ukraine’s Azov Regiment a terrorist organization and that designation could lead to terror charges against some of the captured fighters who made their last stand inside the shattered steel plant in May. Dmytro Kozatski/Azov Special Forces Regiment of the Ukrainian National Guard Press Office via Associated Press

In testimony journalists were allowed to view, witnesses appearing before the Supreme Court supported the proposed terrorism designation, but most of the proceedings were held behind closed doors, so it was not known if any opponents testified.

“I can testify myself that Ukrainian snipers — Azov snipers — really shot civilians trying to escape the city” of Mariupol, Marina Akhmedova of the Presidential Council for the Development of Civil Society and Human Rights testified. “I saw bodies lying on roads with my own eyes. There were many of them, and they were lying probably 10 meters apart from one another. There were no shell craters beside them.”

In a statement, the Azov Regiment dismissed the ruling, accusing the Kremlin of “looking for new excuses and explanations for its war crimes.” It urged the U.S. and other countries to declare Russia a terrorist state.

The Azov soldiers played a key part in the defense of Mariupol, holding out for weeks at the southern port city’s steel mill despite punishing attacks from Russian forces. Ukrainian President Volodymyr Zelenskyy hailed them and the other defenders as heroes.

Moscow has repeatedly portrayed the Azov Regiment as a Nazi group and accused it of atrocities, but has produced little evidence in public.

The regiment, a unit within Ukraine’s National Guard, has a checkered past. It grew out of a group called the Azov Battalion, formed in 2014 as one of many volunteer brigades assembled to fight Russia-backed separatists in eastern Ukraine. The battalion drew its initial fighters from far-right circles.

While its current members have rejected accusations of extremism, the Kremlin has seized on the regiment’s right-wing origins to cast Russia’s invasion as a battle against Nazi influence in Ukraine. Russian state media has repeatedly shown what it claimed to be Nazi insignias, literature and tattoos associated with the regiment.

Last week, dozens of Ukrainian POWs, including Azov fighters from the steel plant, were killed in an explosion at a prison barracks in Olenivka, an eastern town controlled by pro-Russian separatists. Moscow and Kyiv have blamed each other for the blast, with Kyiv saying Russia blew up the barracks to cover up torture against the POWs.

Meanwhile, the first cargo ship loaded with grain to leave Ukraine since Russia invaded more than five months ago approached Istanbul on Tuesday en route to Lebanon, testing an agreement Moscow and Kyiv signed last month to unblock Ukraine’s agricultural exports and ease a global food crisis.

A Ukrainian soldier stands inside the ruined Azovstal steel plant prior to surrender to the Russian forces in Mariupol, Ukraine, on May 16. Dmytro Kozatski/Azov Special Forces Regiment of the Ukrainian National Guard Press Office via Associated Press

An estimated 20 million tons of grain have been stuck in Ukraine since the start of war. The U.N.-brokered agreement to release the grain calls for the establishment of safe corridors through the mined waters outside Ukraine’s ports.

The Razoni, which set sail from the Black Sea port of Odesa on Monday with more than 26,000 tons of corn, was scheduled for inspection Wednesday in Istanbul by a team of Russian, Ukrainian, Turkish and U.N. officials, as part of the deal.

More ships from Ukraine are expected to follow. At Odesa alone, at least 16 more vessels, all blocked since Russia’s invasion on Feb. 24, waited their turn, Ukrainian authorities said.

Global food prices have been soaring in a crisis blamed on the war, global supply chain problems and COVID-19. While Ukraine is a major supplier of grain to the rest of the world, the agreement may not make much of a dent in world hunger.

Most of the grain stuck in Ukraine is to feed livestock, according to David Laborde, an expert at the International Food Policy Research Institute in Washington. Only 6 million tons is wheat, and just half of that is for human consumption, Laborde said. He said Monday’s shipload is chicken feed.

“A few ships leaving Ukraine is not going to be a game changer,” he said.

The ship’s departure came against a backdrop of continued fighting, especially in southern and eastern Ukraine.

In other developments Tuesday:

• American basketball star Brittney Griner was back in court for her trial for cannabis possession. Prosecutors called a narcotics expert who analyzed the substance found in Griner’s luggage. The defense called a specialist who challenged the analysis as flawed. If convicted, she could get 10 years in prison, though the U.S. has proposed a prisoner swap to win her release.

• A train carrying evacuees from the Donetsk region arrived in Kropyvnytskyi in central Ukraine, beginning what Ukrainian authorities described as a compulsory evacuation in the east. Authorities expect to evacuate 200,000 to 220,000 people from the Donetsk region before the fall.

• Russian Defense Minister Sergei Shoigu claimed his country’s forces have destroyed six of the more than dozen HIMARS rocket launcher systems that the U.S. has supplied to Ukraine. Ukraine issued no immediate comment. The launchers have given the Ukrainians more accurate, longer-range firepower.