Just out from Reuters:

INTERFAX UKRAINIAN DEFENCE MINISTRY AS SAYING RUSSIAN FLEET HAS GIVEN UKRAINIAN FORCES IN CRIMEA UNTIL 0300 GMT TOSURRENDER OR FACE STORM

More from Reuters:

Russia's Black Sea Fleet has told Ukrainian forces in Crimea to surrender by 5 a.m. (0300 GMT) on Tuesday or face a military assault, Interfax news agency quoted a source in the Ukrainian Defence Ministry as saying. The ultimatum, Interfax said, was issued by Alexander Vitko, the fleet's commander. The ministry did not immediately confirm the report and there was no immediate comment by the Black Sea Fleet, which has a base in Crimea, where Russian forces are in control. "If they do not surrender before 5 a.m. tomorrow, a real assault will be started against units and divisions of the armed forces across Crimea," the agency quoted the ministry source as saying.

And the response from the Ukraine:

Head of Russian Black Sea Fleet demanded Ukrianian ship give up weapons and surrender, Oleksiy Kirchkov, deputy commander of Ukraine Navy vessel Ternopil, tells Ukraine’s Channel 5 by phone.

Russia set 5 a.m. deadline for 2 Ukraine ships near Sevastopol to capitulate: Channel 5

Ukraine ships “declined to meet the ultimatum, will stay till the very end”

It appears Putin is still unaware of the "costs" he is facing.

Meanwhile:

#Crimea The Russian deadline of 4 o'clock for Ukrainian troops to vacate Belbek base has passed. No sign of Russian military eviction force — Elizabeth Palmer (@elizapalmer) March 3, 2014

Interpreter notes that Ukraine’s first president, Leonid Kravchuk, who served between 1991 and 1994, wrote in the Russian publication Snob.ru today that this crisis could spark World War III: