"Intelligence reports said authorities and a number of well-known public organizations in Ukraine plan actions against the Black Sea Fleet's navigation and hydrographic support facilities," said Cap. 1st Rank Igor Dygalo, an aide to Russia's navy commander.
Dygalo said the fleet is enhancing security measures at the facilities to ensure their uninterrupted operation and safe navigation.
The official said that such provocative actions would be illegal and in breach of the 1997 agreements on the lease by Russia of its Black Sea Fleet's naval base in the Crimean port of Sevastopol.
He added that such steps, if implemented, would harm talks in a Russian-Ukrainian sub-commission on the operation of the Russian Black Sea Fleet in Ukraine.
"The purpose of this sub-commission is to discuss any problems that might occur in a civilized manner. Decisions by local Ukrainian judicial institutions have no legal power in relation to Russian Black Sea Fleet facilities, and attempts by public movements and organizations to obstruct the operation of these facilities would cause extra tension in the region, where the Black Sea Fleet is located," Dygalo said.
Frequent disputes have flared up between Russia and Ukraine over the lease of naval facilities on the Crimean peninsula. Ukrainian bailiffs have made several attempts to seize the headquarters of the Russian fleet's hydrographic service in Sevastopol and radio navigation facilities over the last few years.
The ownership of lighthouses, and the rent Russia pays for them, is one of the main ongoing disputes between the ex-Soviet neighbors.
Under bilateral agreements, Russia's Black Sea Fleet uses the Sevastopol base until 2017. Ukrainian President Viktor Yushchenko recently announced that Ukraine would not extend the lease beyond the date.
In early June, Russia's lower house of parliament adopted a resolution saying the Russian-Ukrainian cooperation treaty could be denounced if Ukraine joins NATO.
To Russia's annoyance, Ukraine's pro-Western leadership has been pursuing NATO membership since Yushchenko's 2004 election. Ukraine failed to secure an agreement on a NATO Membership Action Plan, a key step toward joining the alliance, at the organization's summit in April, but was told the decision would be reviewed in December.