WASHINGTON, April 8 - U.S. Secretary of State John Kerry accused Russian agents and special forces on Tuesday of stirring separatist unrest in eastern Ukraine, saying Moscow could be trying to prepare for military action as it had in Crimea, Reuters reported.

Armed pro-Moscow protesters were still occupying Ukrainian government buildings in two cities in the largely Russian-speaking east on Tuesday, although police ended a third occupation in a lightning night-time operation.

Ukraine's security service said separatists occupying the security headquarters in Luhansk had planted bombs in the building and were holding as many as 60 hostages. Activists in the building denied they had explosives or hostages, but said they had seized an armory full of automatic rifles.

The Ukraine government says the occupations that began on Sunday are part of a Russian-led plan to dismember the country. Kerry said he feared Moscow might repeat its Crimean operation.

"It is clear that Russian special forces and agents have been the catalyst behind the chaos of the last 24 hours," he said in Washington, and this "could potentially be a contrived pretext for military intervention just as we saw in Crimea."

Moscow annexed the Black Sea peninsula last month after a referendum staged when Russian troops were already in control.

Earlier, Russian Foreign Minister Sergei Lavrov dismissed Western accusations that Moscow was destabilizing Ukraine, saying the situation could improve only if Kiev took into account the interests of Russian-speaking regions.

Russia, Ukraine, the United States and the European Union will hold a ministerial meeting next week to discuss the Ukraine crisis, the EU said on Tuesday.

The meeting, to be held at a still unspecified location in Europe, will involve Kerry, Lavrov, EU foreign policy chief Catherine Ashton and Ukraine's foreign minister, Andriy Deshchytsia.

The U.S. State Department said Kerry and Lavrov in a phone call on Monday discussed convening direct talks among the parties to try to defuse tensions.

Shots were fired, a grenade thrown and 70 people detained as Ukrainian officers ended the occupation in the city of Kharkiv during an 18-minute "anti-terrorism" action, the Interior Ministry said.

But elsewhere in Ukraine's eastern industrial heartland, activists armed with Kalashnikov rifles and protected by barbed-wire barricades vowed there was no going back on their demand for a vote on returning to Moscow rule.

Britain expressed fears that Russia wanted to disrupt the run-up to presidential elections next month in Ukraine, which has been ruled by an interim government since the overthrow of Moscow-backed President Viktor Yanukovych in February.

In Kiev, Interior Minister Arsen Avakov partly pinned responsibility for the Kharkiv occupation on Russian President Vladimir Putin. "All this was inspired and financed by the Putin-Yanukovych group," he said.

An aide said police went in when the protesters failed to give themselves up and surrender their arms. Officers did not open fire, despite shooting and the grenade attack from the other side, he said. One police officer was badly wounded and some others less seriously hurt.

Russia has warned Kiev against using force to end the occupations, but authorities may have decided not to give Moscow an excuse to intervene, holding back in the hope that the protests will fizzle out.

In London, British Foreign Secretary William Hague said the occupations bore "all the hallmarks of a Russian strategy to destabilize Ukraine.

The West has expressed concern about what it says has been a buildup of Russian forces along the border with Ukraine. Moscow has said the troops are merely taking part in exercises, but NATO Secretary-General Anders Fogh Rasmussen urged caution.

"If Russia were to intervene further in Ukraine it would be a historic mistake," he told a news conference in Paris. "It would have grave consequences for our relationship with Russia and would further isolate Russia internationally." (rt/ez)