Ukraine is drawing up plans to withdraw its soldiers and their families from Crimea, Kiev's security and defence chief says.
Andriy Parubiy said they wanted to move them "quickly and efficiently" to mainland Ukraine, the BBC reports.
Earlier, pro-Russian forces seized two naval bases - including Ukraine navy's headquarters - in Crimea. AFP reports Ukraine's naval commander was captured in one of the raids.
The seizures came a day after Crimean leaders signed a treaty with Moscow absorbing the peninsula into Russia.
Ukraine has given the pro-Russian authorities in Crimea three hours to release the head of its navy or face a response, the BBC is reporting. Sergiy Gayduk was appointed after his predecessor switched allegiance in favour of Crimea's pro-Kremlin authorities at the start of the month
Acting president Oleksandr Turchynov says commander Gayduk and all the other military and civilian hostages being held in Crimea have to be freed.
The BBC's correspondent in Sevastopol says just a few Ukrainian servicemen are holding out inside the headquarters.
A referendum in Crimea on Sunday, approving its split from Ukraine, came nearly a month after Kiev's pro-Russian President Viktor Yanukovych was replaced by Western-leaning interim authorities.
The BBC says Mr Parubiy set out more details in a news conference on Kiev's position in light of the events in Crimea.
"We are developing a plan that would enable us not only to withdraw servicemen but also members of their families in Crimea, so that they could be quickly and efficiently moved to mainland Ukraine," he said.
He also said arrangements were now being set up to introduce visas for Russian nationals travelling to Ukraine.
AFP reports dozens of despondent Ukrainian soldiers - one of them in tears - filed out of the Ukraine's main navy headquarters in the historic Black Sea port city of Sevastopol on Wednesday after it was stormed by hundreds of pro-Kremlin protesters and masked Russian troops.
A regional prosecutor's statement told AFP the commander was detained because he was suspected of "ordering Ukrainian military units... to open fire on peaceful civilians".
Defence ministry officials said Russian forces also seized a military base in Crimea's western port town of Novoozerne after using a tractor to ram open its main gate.
An AFP reporter saw about 50 Ukrainian servicemen file out of the base under the watchful eye of Russian soldiers, while pro-Moscow militias lowered the Ukrainian flag.
Washington has condemned the Russian seizure of Ukrainian military installations, saying they are creating a dangerous situation.
Ukraine has proposed Crimea be declared a demilitarised zone by the United Nations, with a pullout by both Russian and Ukrainian troops.