SEVASTOPOL, Crimea (AP) -- Senior Ukrainian officials planned to travel to Crimea on Wednesday in a bid to avert an escalation in hostilities, a day after two men were killed at a military facility in a gunbattle between Ukrainian troops and a militia loyal to the local government.
The prime minister in Crimea, which was nominally incorporated into Russia on Tuesday, said Ukraine's deputy prime minister and defense minister would be turned back, however.
"They are not welcome in Crimea," Sergei Aksyonov was quoted as saying by Interfax news agency. "They will not be allowed to enter in Crimea. They will be sent back."
Ukraine's military is heavily outnumbered in Crimea, with tens of thousands of Russian-led forces patrolling the peninsula. In a further sign of that, Crimea militias stormed the Ukrainian navy headquarters in the Black Sea port of Sevastopol, taking it over without resistance.
An Associated Press photographer said several hundred militiamen took down the gate and made their way onto the base. They then raised the Russian flag on the square by the headquarters.
The unarmed militia waited for an hour on the square before the move to storm the headquarters. Following the arrival of the commander of the Russian Black Sea fleet, the Crimeans took over the building.
The AP photographer was able to enter the headquarters and saw the militia roaming around while the Ukrainian servicemen were packing up and leaving.
On Tuesday, President Vladimir Putin signed a treaty to incorporate Crimea into Russia following a referendum Sunday in which residents of the region overwhelmingly backed the move.
Jubilant crowds in Moscow and other cities across Russia hailed the annexation, while Ukraine's new government called Putin a threat to the "civilized world and international security," and the U.S. and the European Union threatened tougher sanctions against Moscow. On Monday, Washington and Brussels targeted Russian and Crimean officials with visa bans and asset freezes.
Russian news agencies on Wednesday cited Constitutional Court chairman Valery Zorkin as saying the treaty signed by Putin has been ruled valid, thus formally clearing another hurdle for Moscow to annex Crimea. The treaty now only requires ratification by the Russian parliament.
A Ukrainian serviceman and a member of a militia were killed by gunfire in the incident in Crimea on Tuesday.
It is unclear whether the militiaman was a Ukrainian citizen. Although Moscow has insistently denied it has not deployed its own troops in Crimea, people in the peninsula have reported seeing a large number of military vehicles with Russian plates.
Thousands of troops under apparent Russian command took over Crimea two weeks before Sunday's hastily called referendum, seizing Ukrainian military bases, blockading others and pressuring Ukrainian soldiers to surrender their arms and leave.
Putin insisted Russia's military presence in Crimea was limited to those stationed under the terms of a treaty with Ukraine that allows Russia to have up to 25,000 troops at its Black Sea fleet base. Ukraine claims that Russia deployed further forces, however, and expressly went against its request for troops to remain confined within their barracks.
AP writer Peter Leonard contributed to this report from Kiev, Ukraine.