Kiev said it was dispatching its defense minister but Crimea's regional leader said he would be barred from entry amid mounting tensions in a region at the epicenter of the worst East-West standoff since the Cold War.

Dozens of despondent Ukrainian soldiers filed out of the Ukraine's main navy base in the Black Sea port city of Sevastopol after its storming by hundreds of pro-Kremlin protesters and Russian troops.

A Russian forces' representative said that Ukraine's navy commander Sergiy Gayduk -- appointed after his predecessor switched allegiance in favor of Crimea's pro-Kremlin authorities at the start of the month -- had been detained.

"He was blocked and he had nowhere to go. He was forced out and he has been taken away," Igor Yeskin told reporters.

A Defense Ministry spokesman in Crimea said pro-Russian forces also seized the checkpoint set up in front of a Ukrainian military base in the region's western port town of Novoozerne.

He said they used a tractor to ram open the gate and were now in a standoff with Ukrainian troops.

The Ukrainian government dispatched acting Defense Minister Igor Tenyukh and First Deputy Prime Minister Vitaliy Yarema to the region for urgent mediation talks.

But Crimea's self-declared Prime Minister Sergei Aksyonov told the Interfax news agency while on a visit to Moscow that "no one will let them into Crimea and they will be sent back."

Russia’s President Vladimir Putin had brushed aside global indignation and Western sanctions on Tuesday to sign a treaty absorbing Crimea and expanding Russia's borders for the first time since World War II.

Russia's Constitutional Court ruled unanimously on Wednesday that the "treaty complies with the Russian Constitution."

The historic and hugely controversial moment came less than a month after the ouster in Kiev of a Moscow-backed government by leaders who spearheaded three months of deadly protests aimed at pulling Ukraine out of the Kremlin's orbit for the first time.

BA/BA