Russian forces backed up an ultimatum issued Monday to Ukrainian sailors in the Crimea to surrender and give up their ships or face attack, Ukrainian military spokesmen said.
The ultimatum with a deadline of early Tuesday morning followed a dramatic confrontation in which Ukrainian sailors at a Crimean base surrounded by Russian troops pledged their allegiance to Ukraine and rejected pleas to defect from renegade Ukrainian Rear Adm. Denis Berezovsky.
Four ships from Russia's Black Sea fleet were blocking the Ukrainian anti-submarine warship Ternopil and the command ship Slavutych from leaving dock in Crimea's Sevastopol harbor following the demand to defect from Crimean Regional Prime Minister Sergey Aksyonov, a Moscow ally, the Associated Press reported.
There were no immediate reports of clashes between Ukrainians loyal to the new government in Kiev and Russian forces in Crimea. However, Aksyonov declared the creation of "Crimea's Naval Forces" and said that Berezovsky was the naval chief.
"The Republic will have its own Navy, which will be commanded by Rear Adm. Berezovsky," Aksyonov told reporters.
Aksyonov ordered Ukrainian sailors to "disregard any commands coming from Ukraine's new self-proclaimed authorities" and warned them not to take orders "for using arms until my personal instructions."
Ukrainian officials charged that Vice Admiral Aleksandr Vitko, commander of Russia's Black Sea fleet, went aboard one of the blockaded Ukrainian ships and ordered the crew to "swear allegiance to the new Crimean authorities, or surrender, or face an attack."
At Ukraine's naval command on Monday morning, officers lined up in the yard of their Sevastopol headquarters, where they were addressed first by Berezovsky and then by the newly-appointed Ukrainian naval commander, Serhiy Haiduk.
The officers broke into applause as Haiduk read them an order from Kiev removing Berezovsky from his position, and told them that Berezovsky was facing treason charges, the Guardian newspaper reported.
"I know my men will stay loyal to their oaths," Haiduk said before the address. "What Berezovsky has done is a matter for him alone. When he brought intruders in here, we did not offer armed resistance as would have been our right, in order to avoid any provocations the other side would like."
In Moscow, Russian officials dismissed reports of surrender demands and naval blockades as "complete nonsense," Russia's Interfax news agency reported.
The escalating tensions in Russian-speaking eastern Ukraine followed the ouster last month of ouster of Ukrainian President Victor Yanukovych, who was backed by Russian President Vladimir Putin.
Putin has since ordered massive military exercises on Ukraine's borders and Russian troops in the Crimea have moved out of their bases in what Ukraine's new government has charged is an occupation of the regional republic.
A senior U.S. administration official told CNN that Russian forces "have complete operational control of the Crimean Peninsula." The official said the U.S. estimates there are 6,000 Russian ground troops backed up by 15,000 sailors with the Black Sea fleet.
Secretary of State John Kerry was due to arrive Tuesday in Kiev in a show of support for the embattled new government. If Putin's provocations continue, Ukraine will "fight," Kerry said Sunday on CBS' Face the Nation.
Kerry called Putin's actions "an incredible act of aggression against the sovereignty of Ukraine."
Also appearing on "Face the Nation," Defense Secretary Chuck Hagel said "this could be a very dangerous situation if this continues in a very provocative way. We have many options, like any nations do. We're trying to deal with the diplomatic focus."
Ukraine Prime Minister Arseniy Yatsenyuk pleaded on Monday for help from the West and stressed that Crimea remained part of Ukraine.
"Any attempt of Russia to grab Crimea will have no success at all. Give us some time," Yatsenyuk said at a news conference with British Foreign Secretary William Hague in the Ukrainian capital of Kiev.
-- Richard Sisk can be reached at email@example.com