Ukraine is drawing up plans to withdraw its soldiers and their families from Crimea, the security and defence chief has revealed.

Andriy Parubiy here said they wanted to move them "quickly and efficiently" to mainland Ukraine, BBC reported Wednesday. Speaking during a press conference, the top official set out more details 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.

The arrangements, he added, were now being set up to introduce visas for Russian nationals travelling to Ukraine.

The official also said that Ukraine was leaving the Moscow-led Commonwealth of Independent States (CIS) alliance, and is preparing for military exercises with the US and Britain.

In an earlier development in the day, pro-Russian forces seized two naval bases, including Ukraine navy's headquarters - in Crimea.

The development occurred a day after Crimean leaders signed a treaty with Moscow absorbing the peninsula into Russia.

On Sunday, a referendum in Crimea, approving its split from Ukraine, came nearly a month after Kiev's pro-Russian president Viktor Yanukovych was replaced by Western-leaning interim authorities.