KIEV/SEVASTOPOL -- Ukraine has lodged criminal proceedings againt Admiral Alexander Vikto, commander of Russia's Black Sea Fleet, Ukrainian Prosecutor General Maher Magnitsky announced on Wednesday.

Vikto will be charged of abetting "the betrayal of the country" and "organizing sabotages", Magnitsky said in a local live broadcast television program.

Vikto is the leader of Russia's Black Sea Fleet and a Russian citizen, he said, while Ukraine's Prosecutorate said Vikto is sued because he "committed crimes on Ukraine's territory".

The Ukrainian defense Ministry claimed Vikto once issued an ultimatum to the Ukrainian troops, asking Ukrainian soldiers to surrender before 5:00 a.m. on Tuesday, or they would face Russian troops' attack.

The command of the Black Sea Fleet said in response that Ukraine's claim was "pure nonsense" and Russia "was used to Ukraine's absurd accusations."

Russia's Black Sea Fleet is based in Sevastopol, the western city-port of Ukraine's autonomous republic of Crimea, which has become the epicenter of the ongoing crisis in Ukraine since President Viktor Yanukovych was ousted by the parliament on February 22.

Since the outbreak of the Crimea crisis, the Ukrainian government and military have been accusing Russia of deteriorating the situation by increasing troops in Crimea.

According to the Ukrainian defense Ministry, Russia has sent some 5,500 special task troops into Ukraine after the Crimea crisis broke out, and currently there were a total of 16,000 Russian soldiers in Ukraine, including the Black Sea Fleet, which "rudely breached" the pact between the two countries on the Black Sea Fleet naval base in Ukraine.

But a Russian military expert said Tuesday that current Russian troop movements in Crimea was nothing unusual and could not be described as aggression.

Moscow had a right to deploy up to 25,000 troops in Crimea in line with agreements signed with Kiev as long ago as the mid-1990s, and currently there were only 18,000, Vladimir Kozin, chief of the advisers group to the director of the Russian Strategic Research Institute, told Xinhua.

"Those troops have been deployed there long before the recent events. And they may legally stay there until 2042. So they pose no threat to Ukraine," said Kozin, who is also a Russian Academy of Military Sciences professor.

All Russian troops deployed in Crimea were attached to the Black Sea Fleet, in accordance with agreements signed between Moscow and Kiev following the breakup of the Soviet Union, the expert said.

According to the agreements, Russia has a right to move its personnel between its coastal facilities, for example from Kerch to Sevastopol in Crimea.

In Sevastopol, both Ukraine and Russia possess military naval bases.Two Ukrainian ships were seen anchored at Streletskiy Bay on Wednesday and blocked by Russian vessels.

As Xinhua reporters witnessed, the situation seemed calm in the city. However, there were fully equipped Russian military servicemen in front of the military objects there.

The situation was same in front of the Ukrainian Navy Headquarters in the city, and Ukrainian soldiers said they guarded against possible provocations.

The road to Belbek Airport, 25 km northwest of Sevastopol was blocked by Russian soldiers and military personnel vehicles, supported by local unidentified paramilitaries.