KIEV (Reuters) - Ukraine's authorities plan to launch a "full-scale anti-terrorist operation" involving the army against pro-Russian separatist militants, the acting president said on Sunday, as the United States envoy to the United Nations said her country was prepared to step up sanctions against Moscow if pro-Russian military actions in eastern Ukraine continue.
Mr Oleksander Turchinov said in a televised address to the nation that Russia was waging a war against Ukraine by sowing disorder in the east of the country, but he offered not to prosecute any militants who gave up their weapons by Monday morning.
Referring to the death of a state security officer and the wounding of other members of law-enforcement bodies in an earlier clash with pro-Russian militants near the town of Slaviansk, he said: "The blood of Ukrainian heroes has been shed in a war which the Russian Federation is waging against Ukraine. The aggressor has not stopped and is continuing to sow disorder in the east of the country." He was referring to a rash of attacks on state buildings by pro-Russian militants in towns in Russia-speaking areas of the east.
Meanwhile, American ambassador to the UN Samantha Power said on ABC's This Week programme that the latest events in Ukraine bore "the telltale signs of Moscow's involvement". She said sanctions already imposed by Washington have had an impact: the Russian rouble has fallen to an all-time low, the country's stock market has depreciated by 20 per cent and investors are fleeing the country.
"The president has made clear that, depending on Russian behavior, sectoral sanctions in energy, banking, mining could be on the table, and there's a lot in between," Ms Power said.
"I think we've seen that the sanctions can bite, and if actions like the kind we've seen over the last few days continue, you're going to see a ramping up of those sanctions."
The sanctions have been the most visible sign of US anger at Russia's annexation of the Crimea region in southern Ukraine last month, reflecting the deepest plunge in US-Russian relations since the Cold War.
Ukraine now faces a rash of rebellions in the east that it says are inspired and directed by the Kremlin.
Kiev authorities say the separatists rebellions have been inspired and directed by the Kremlin, a charge Moscow denies.
"The National Security and Defence Council has decided to launch a full-scale anti-terrorist operation involving the armed forces of Ukraine," he declared.
"We will not allow Russia to repeat the Crimean scenario in the eastern regions of the country," referring to Moscow's annexation of the peninsula following its takeover by pro-Russian militants.
Pro-Russian activists seized government buildings on Saturday in the eastern town of Slaviansk, about 150km from the Russian border. Ukrainian security forces were trying to oust the activists, who set up barricades on the outskirts of the city.
Asked on ABC if Russian President Vladimir Putin wants to seize eastern Ukraine, Ms Power said his actions "give credence to the idea". Though Russians are insisting that is not what Moscow wants, she said: "Everything they're doing suggests the opposite."
Nato described the appearance in eastern Ukraine of men with specialized Russian weapons and identical uniforms without insignia - as previously worn by Moscow's troops when they seized Crimea - as a "grave development".
Ms Power said the rebellion has "all the telltale signs of what we saw in Crimea: It's professional, it's coordinated, there's nothing grassroots-seeming about it. The forces are doing in each of the six or seven cities that they've been active in exactly the same thing".
Republican Senator John McCain, a frequent critic of US policy on Ukraine, said on CBS that the Obama administration's failure to punish Russia over Crimea has only emboldened Putin. "The question is now, What do we do and what does he do?" McCain said on the Face The Nation programme.
"It's obvious that he is encouraged by the fact that we sanctioned a few people and suspended - didn't even throw him out - of the G8."
Sen McCain repeated his calls for tougher sanctions and for giving Ukrainians light weapons so they can defend themselves.
"They didn't fight in Crimea," he said. "But if he starts moving in further encroachment in this way into eastern Ukraine, they will fight."
The United States on Friday imposed sanctions on a Crimea-based gas company, Chernomorneftegaz, effectively putting it off limits to Russia's state-controlled Gazprom, which was expected to bid for a stake in the company.
The move, along with penalties on six Crimean separatists and a former Ukrainian official, is the third round of US sanctions since the Ukraine crisis erupted.