Ukraine said one of its soldiers had been killed in Crimea Tuesday in the first case of bloodshed since Russian troops and pro-Kremlin militia seized the rebel peninsula almost three weeks ago.
Regional defence ministry spokesman Vladislav Seleznyov told AFP the soldier had died after being shot in the neck when a group of gunmen stormed a Ukrainian military base in the northeast of Crimea's main city of Simferopol.
Seleznyov did not specify whether the base was stormed by Russian soldiers or pro-Kremlin militia who also patrol the peninsula.
The spokeman said another soldier was wounded in the attack.
Russian President Vladimir Putin on Tuesday signed a treaty claiming the Black Sea region of Crimea as Russian territory, setting of a firestorm of condemnation from Kiev and the West.
Russian forces had seized the peninsula Crimea at the beginning of March after the toppling last month of the pro-Kremlin regime in Ukraine and the rise to power of a new Western-backed administration that is seeking closer ties with the European Union.
Ukraine's Prime Minister Arseniy Yatsenyuk told an emergency government session in Kiev that his country's conflict with Russia was entering a "military stage".
"The conflict is shifting from a political to a military stage," Yatsenyuk told a nationally televised meeting that was also attended by acting president Oleksandr Turchuynov.
"Russian soldiers have started shooting at Ukrainian military servicemen, and that is a war crime."
Ukraine's navy chief Sergiy Gayduk said that an officer had been shot and injured in the leg "during an attack against a base in Simferopol."
He did not specify where or when the incident happened or who was behind the attack.
But an AFP reporter outside a Ukrainian military unit in a suburb northeast of Simferopol heard a burst of gunfire coming from the building and saw two ambulances driving into the area
The region around the military unit was sealed off by what appeared to be pro-Moscow militants.
"Armed attempts to take over (Ukrainian) military units have multiplied in recent days," Gayduk said at the government meeting.