Russia and Ukraine exchanged 10 prisoners of war each on Thursday in what Ukrainian Deputy Prime Minister Iryna Vereshchuk called the first full-fledged swap of the month-old conflict.

The exchange also freed 19 Ukrainian civilian sailors who were captured as their ship tried to take Ukrainian troops off of Snake Island in late February.

Ukraine released 11 Russian civilian sailors as part of the deal, Vereshchuk said as she announced the transfer. The civilians had been rescued from a ship that sank near Odesa, she said.

Russia's takeover of Snake Island, also known as Zmiinyi Island, was much-discussed in the first days of the war after Ukrainian soldiers at the small military outpost in the Black Sea defied threats from a looming Russian vessel by flatly telling it, "Russian warship. Go f*** yourself."

The soldiers were initially feared to have been killed, but Russian state media later reported that they had been taken prisoner.

It wasn't immediately clear whether any Ukrainian soldiers from the island outpost were among the captives who were exchanged on Thursday — but Ukraine's border guard agency said earlier in the day that Vereshchuk was working to free soldiers who had been on Snake Island.

The Ukrainian civilian sailors freed by Russia had been aboard the Sapphire, a ship that sailed to the island on a search and rescue mission but was itself captured. As part of the exchange, Russian forces will release their ship, sending it to a dock in Turkey, Vereshchuk said.

Ukraine and Russia have engaged in at least two smaller prisoner exchanges in the month-old war, including the swap of nine Russian servicemen for Melitopol Mayor Ivan Fedorov.

And on March 1, Ukraine's military said it exchanged a captured Russian military police officer for five Ukrainian soldiers in Sumy, an oblast in northeastern Ukraine.

This story originally appeared on the Morning Edition live blog.

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