KIEV, Ukraine - In defiance of the U.S. and the European Union, Russia tightened its stranglehold over Crimea on Monday as Ukraine accused it of piracy by blocking two of the besieged country's warships and ordering them to surrender or be seized.
The West struggled to find a way to get Moscow to back down, but with little beyond already threatened diplomatic and economic sanctions, global markets fell sharply over the prospect of violent upheaval in the heart of Europe.
For its part, Moscow reiterated its price for ending the conflict: the restoration, pending new elections, of a government in Kiev that represents pro-Russian as well as Ukrainian interests.
Some 16,000 Russian troops have been deployed in the strategic Crimean region, Ukraine's mission to the United Nations said Monday, as fears grew in the Ukrainian capital and beyond that the Kremlin might carry out more land grabs in pro-Russian eastern Ukraine, adding urgency to Western efforts to defuse the crisis.
U.S. Secretary of State John Kerry was headed to Kiev in an expression of support for Ukraine's sovereignty, and the EU threatened a raft of punitive measures as it called an emergency summit on Ukraine for Thursday.
But it was Russia that appeared to be driving the agenda.
Foreign Minister Sergey Lavrov said at a U.N. Human Rights Council session in Geneva that Ukraine should return to an agreement signed last month by pro-Russian President Viktor Yanukovych - but not Moscow - to hold early elections and surrender some powers. Yanukovych fled the country after sealing the pact with the opposition and foreign ministers of France, Germany and Poland.
"Instead of a promised national unity government," Lavrov said of the fledgling new administration in Kiev, "a government of the victors has been created."
Meanwhile, Ukrainian authorities said that Russian troops had issued an ultimatum for two Ukrainian warships to surrender or be seized - prompting the country's acting president to accuse Russia of "piracy."
"I call on the leadership of the Russian Federation. Stop the aggression, stop the provocations, stop the piracy! These are crimes, and you will be called to account for them," acting president Oleksandr Turchynov said.