Thirteen Ukrainian border guards defending a tiny island in the Black Sea from the Russian military were killed Thursday.

The soldiers were on Zmiinyi Island in the Odesa region when it was approached by two Russian vessels, according to Ukrainian media outlets.

In an audiotape obtained by CNN, the Ukrainian soldiers were told by an officer of the Russian Navy to "lay down your weapons" or "be bombed."

The Washington Post reported that the Ukrainian soldiers responded back bluntly in a final display of defiance, “Russian warship, go f–k yourself.”

The news outlets reported that the warship then opened fire, killing all 13 border guards.

The island was then taken over by the Russians, The Post reported.

On Friday, Zelenskyy said during a press briefing that the guards died "heroes" and would be posthumously awarded the title of Hero of Ukraine.

Along with the soldiers, the president added that 137 people were killed, and 316 were injured on the first day of the attack.