Ukraine was concerned after several Black Sea Fleet warships based in Crimea dropped anchor off the Georgian coast during and after Moscow's armed conflict with Tbilisi over breakaway South Ossetia in August.
Under bilateral agreements, Russia's Black Sea Fleet has the use of the Sevastopol base and other naval facilities in Crimea until 2017. Ukraine's pro-NATO government is seeking Russia's withdrawal from the base after the agreements expire, while Russia wants to extend the lease.
The Ukrainian Navy press service said the commander-in-chief had set the task of beefing up the military group in Sevastopol.
"We are not going to wage war against Russia, but Ukraine will not let the South Ossetian scenario happen in Crimea, and the Navy will complete the objectives set by the commander-in-chief, and has all resources to do so," a press service spokesman said.
"The marine group will be increased by 1,500 people, and the Kamyshovaya Bay, the village of Kacha and Balaklava are preliminarily being considered for the deployment of three air defense units," a naval officer said on condition of anonymity. "This will allow control of the entire air space extending to Simferopol and prevent a possible seaborne assault."
According to the source, servicemen from Ukraine's western regions, "being genuine patriots," will account for 80% of these forces.
Southern and eastern Ukraine, including Crimea, are predominantly Russian-speaking and supported the pro-Russian Viktor Yanukovich in the 2004 election and subsequent "Orange Revolution" that brought the pro-Western Viktor Yushchenko to the presidency.
Vladimir Tyunin, the chairman of the Sevastopol branch of Ukraine's Russian Bloc party said the plans to enlarge the marine group were aimed at pacifying pro-Russian Crimea residents discontented with Kiev's policies. Protests against NATO's presence in Crimea are frequent in Sevastopol.
"Defense Ministry officials fear that whole units would refuse to shoot at civilians in the event of a conflict, but guys from Lvov will not," he said referring to a town in western Ukraine, notorious for its anti-Russian sentiments.
According to polls, most Ukrainians do not support the idea of their country joining NATO.