Ukraine has accused Russia of stirring up anti-US and anti-Nato protests on the Crimean peninsula where Russia's Black Sea Fleet is based.
The allegation - made by the Our Ukraine party of President Viktor Yushchenko - follows a week of anti-Nato protests in Crimea that appear to have caught the government unawares.
Emotions are running high ahead of a multinational military exercise on the peninsula, called Sea Breeze, due to begin in July.
Coaches carrying US Marine reservists have been stoned, the Ukrainian Socialists have demanded the resignation of the Defence Minister, Anatoliy Hrytsenko, and Russian MPs have called for Crimea to be taken away from Ukraine and incorporated into Russia.
The dispute comes as Ukrainian politicians are struggling to form a coalition government more than two months after the election that confirmed the country's apparently irreparable split into pro-Russian and pro-Western camps.
The issue of Nato is divisive; President Yushchenko, the leader of the 2004 "orange revolution", wants his country to move closer towards the EU and Nato with a view to joining both organisations. But while many Ukrainians would be happy to become part of the EU, two-thirds of the 47 million population is strongly opposed to joining Nato.
Pro-Russian forces believe it would be "high treason" to join Nato and feelings run particularly high in Russian-speaking Crimea where Russia's Black Sea Fleet is based as a hangover from the Soviet-era.
Many locals feel closer to Moscow than Kiev and want the Russian base at Sevastopol to remain. The pro-Western "orange" politicians running the country have told Moscow they will not renew its lease on the base when it expires in 2017. Anti-Nato and anti-US feelings came to a head at the end of May, when a ship carrying US Marine reservists docked in the Crimean port of Feodosia ahead of Operation Sea Breeze.
The Marines were supposed to help refurbish a Ukrainian naval base for the exercise but their arrival has instead triggered a firestorm of protest that shows no sign of abating. The Marines have been stoned, subject to bomb hoaxes, been trapped in their accommodation, ridiculed in the Russian press, and construction supplies have been blocked at the port. Opposition has been led by die-hard Communists, Russian nationalists and by the neo-Communists, headed by the MP Natalya Vitrenko.
Russian MPs have flown in to offer their support, a development that has prompted Mr Yushchenko to rush through legislation allowing him to deport foreigners taking part in the protests. Pro-Russian forces accused Mr Yushchenko and Nato of planning to build a Nato base in Crimea and of shipping in toxic waste. Both allegations have been denied and the government has suggested Russian special forces have had a hand in whipping up the protests.
The Our Ukraine party went even further yesterday, accusing Moscow of directly fomenting the crisis. "The deliberate incitement of Crimean residents over the multinational military exercises by certain political forces directly supported by Moscow endangers not only the international image of this country, but also the national security and interests of Ukraine," it said in a statement.
It argued that military exercises of the same kind have been held regularly since 1997 and that Russia holds similar exercises too.
Locals have also been outraged by the scenario for this year's exercise; it involves Nato forces restoring order in a breakaway peninsula caught between the clutches of a totalitarian government and a democratic one.