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KIEV — Ukraine’s prime minister said Sunday Russian separatist “ringleaders” trying to destroy Ukraine’s independence would be brought to justice, warning: “The ground will burn under their feet."

"We will find all of them — if it takes one year, two years — and bring them to justice and try them in Ukrainian and international courts. The ground will burn under their feet," said Prime Minister Arseniy Yatsenyuk.

As pro-Russian Crimean leaders staged a referendum for the peninsula to secede to Russia, Yatsenyuk said separatists were trying to destroy Ukrainian independence "under the cover of Russian troops."

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Ukraine’s new leaders announced a plan to raise a force of 20,000 men and urged Ukrainians to sign up to bolster a newly created National Guard.

"It will have training centers, legal weapons will be distributed. You will have the opportunity to defend the country, with the forces of the National Guard and the security forces," Yatsenyuk told a cabinet meeting.

Earlier, acting defense minister Ihor Tenyukh said Russia was pressing ahead with a military build-up in Crimea in violation of an agreement covering basing rights for Moscow's Black Sea fleet, which has been there since Soviet times.

The country's new defense chiefs admit that the army is in poor shape and outgunned and outnumbered by Russian forces. But Andriy Parubiy, head of the National Security and Defense Council, said: "We are trying as quickly as possible to upgrade our armed forces so that they can work effectively."

Instead of an agreed limit of 12,500 Russian servicemen in Crimea, Moscow now had 22,000 there, Tenyukh said.

He later told journalists that the defense ministries in Kiev and Moscow had declared a truce until March 21 during which Russian forces, who have been arriving by boat and helicopter, would leave Ukrainian military facilities untouched.

— Reuters