Russia's lower house of parliament, the State Duma, has overwhelmingly voted to ratify a treaty to annex Crimea from Ukraine.
The lawmakers voted on the measure Thursday, and the parliament's upper house, the Federation Council, will hold a similar vote on Friday.
On Tuesday, President Vladimir Putin and Crimean leaders signed the treaty making Crimea part of Russia after Mr. Putin declared in a speech that the peninsula had always been an "inalienable" part of Russia.
U.N. Secretary-General Ban Ki-moon met Thursday in Moscow with President Putin and Russian Foreign Minister Sergei Lavrov and is expected to meet with Ukraine's acting President Oleksandr Turchynov and acting Prime Minister Arseniy Yatsenyuk on Friday in Kyiv.
Mr. Ban said Thursday that an honest and constructive dialogue between Kyiv and Moscow is essential.
Also Thursday, Ukrainian officials said armed pro-Russian forces seized three Ukrainian warships in the Sevastopol Bay. The Associated Press reported Ukrainian servicemen were seen leaving one of the ships, but no casualties were reported.
Crimeans voted in a regional referendum last Sunday to declare independence from Ukraine in hopes of joining the Russian Federation.
Meanwhile, President Turchynov says the commander of Ukraine's navy has been freed after being held by Russian forces and Crimean authorities at the navy's headquarters in Crimea. He said Rear Admiral Sergei Haiduk was released, along with an unspecified number of civilians.
The group was detained after the Ukrainian naval base in the Crimean port of Sevastopol was seized Wednesday. Reports indicated pro-Russian militiamen, Crimea's so-called "self-defense" forces, were behind the takeover, but President Turchynov's statement suggests Russian forces were also involved.
After the seizure, which faced no resistance from Ukrainian servicemen, Ukraine's security chief said the country has drawn up plans to evacuate its outnumbered military personnel from the Crimean peninsula.
In announcing the withdrawal, Ukraine National Security and Defense Council Secretary Andriy Parubiy said Kyiv will seek U.N. support in turning the peninsula into a demilitarized zone. He also said Ukraine is planning to hold military maneuvers "with our allies," but did not elaborate.
Russian Deputy Defense Minister Yuri Borisov said Thursday Moscow will bolster its "military infrastructure" in Crimea to ensure the peninsula is "a worthy representative of the Russian Federation" and "protected against all possible encroachments."