Ukraine's foreign ministry has been given instructions to introduce visas for Russians visiting Ukraine, the country's security chief Andriy Parubiy said on Wednesday.
Parubiy, secretary of the National Security and Defense Council, also said the Kiev government would appeal to the United Nations to declare Crimea a demilitarized zone and take measures for Russian forces to leave the peninsula.
Speaking at a news conference, he said prospects of military confrontation between Russia and Ukraine were growing and Russia planned to occupy Ukrainian territory and undermine presidential elections.
"A range of measures have been taken in reaction to the actions of Russia ... The foreign ministry has been tasked to introduce a visa regime with the Russian Federation," Parubiy said.
A statement on the website of the Council, a body made up of senior military and security officials, said the meeting was devoted to "the state of Ukraine's national security and measures to neutralize foreign and domestic political threats".
The Council's decisions generally result in a presidential decree which has the force of law.
Ukraine's Prime Minister Arseny Yatsenyuk earlier ordered the first deputy prime minister and the acting defense minister to fly to Crimea to "resolve the situation". But Interfax Ukraine news agency quoted a minister as saying they had not been allowed into the region now held by Russian forces.
Earlier, around a dozen Ukrainian servicemen, unarmed and in civilian clothes, walked out of the Ukrainian naval headquarters in the Crimean port of Sevastopol after it was taken over by pro-Russian forces, a Reuters witness said. Crimeans voted at the weekend to leave Ukraine and join Russia, and the peaceful handover of military facilities to Moscow's control has been a major concern after one Ukrainian was killed in a shooting at a military facility in Crimea's main city Simferopol on Tuesday. Three Russian flags were flying at one of the entrances to Ukraine's naval headquarters in the Crimean port of Sevastopol, suggesting that at least some of the base was under the control of pro-Russian forces. A Reuters witness saw three armed men, possibly Russian soldiers in unmarked uniforms, at the gate where the flags were flying. Meanwhile, acting Defense Minister Ihor Tenyukh said Ukrainian forces will not withdraw from Crimea even though Russian President Vladimir Putin has signed a treaty to make it part of Russia. Asked by journalists on the sidelines of a government meeting if Kiev would pull its forces out of the peninsula, Tenyukh replied: "No. We will stay". US The Truxtun, a U.S. guided-missile destroyer has started a one-day military exercise with the Bulgarian and Romanian navies in the Black Sea on Wednesday, a U.S. Naval Forces official told Reuters on Wednesday. Ukraine's Crimea peninsula juts into the north of the Black Sea. The U.S. military has described it as a "routine" deployment scheduled well before the crisis in Ukraine. "There are many reasons for exercises with allies, it allows us an opportunity to assure our NATO allies that we support them," Shawn Eklund, a public affairs officer for U.S. Naval Forces Europe, told Reuters. Meanwhile, US Vice President Joe Biden said Russia is on a "dark path" to isolation over its actions in Ukraine and the United States will respond to any aggression against NATO allies. Biden made the comments during a trip to Lithuania to reassure Baltic allies worried about what an emboldened Russia might mean for their nations. Lithuania, along with fellow Baltic nations of Latvia and Estonia, are NATO members. Russia Russia accused Western states of violating a pledge to respect Ukraine's sovereignty and political independence under a 1994 security assurance agreement, saying they had "indulged a coup d'etat" that ousted President Viktor Yanukovich last month. The Foreign Ministry said actions by the United States and European Union ran counter to assurances granted by the United States, Britain and Russia in exchange for Ukraine's commitment to give up its nuclear arsenal after the Soviet collapse. UK Britain warned President Vladimir Putin on Wednesday that Russia could face permanent exclusion from the G8 if the Kremlin took further steps against Ukraine. "I think we should be discussing whether or not to expel Russia permanently from the G8 if further steps are taken," Prime Minister David Cameron told the British parliament. Crimea's PM Crimean Prime Minister Sergei Aksyonov said on Wednesday that senior Ukrainian officials dispatched to the region by the government in Kiev amid tension between military forces would not be allowed to enter, Russian news agency Interfax reported. "They are not wanted in Crimea. Nobody will let them into Crimea, they will be sent back," Interfax quoted Aksyonov as saying after Ukrainian Prime Minister Arseny Yatseniuk ordered and the acting defense minister and first deputy prime minister to fly to Crimea to "resolve the situation" in the region now controlled by Russian forces. Germany German Foreign Minister Frank-Walter Steinmeier said on Wednesday he had told his Russian counterpart that a mandate for a mission by Organisation for Security and Cooperation in Europe (OSCE) observers to Ukraine must be agreed within 24 hours. Steinmeier told reporters he had spoken to Russian Foreign Minister Sergei Lavrov and the Chairman of the OSCE and that they had overcome differences on the number of staff to be sent but still had to agree on the regions to be visited. "We need an observer mission now and in my conversations this morning I said agreement on a mandate must take place within the next 24 hours," Steinmeier told a news conference. REUTERS For more details, watch Rita Khoury's full report in the video above