Luxembourg:
Britain called on Monday for "further" European Union sanctions against Russia in response to its "dangerous" escalation of the crisis in eastern Ukraine.
"I will be arguing today that further sanctions have to be the response to Russia's behaviour," British Foreign Secretary William Hague said as he arrived for a meeting of EU foreign ministers.
"There do have to be consequences," Hague said, adding that the events of the last 48 hours are "clearly a further escalation of the crisis ... and clearly a very dangerous one."
He said there could be no "doubt that this has been planned and brought about by Russia," adding that Russian denials of involvement "do not have a shred of credibility."
Moscow's actions, similar to how it had orchestrated Crimea's move to join Russia, meant it was time to discuss additional sanctions to asset freezes and travel bans already imposed on leading business and political figures close to President Vladimir Putin, he said.
Other EU foreign ministers, however, appeared reluctant to toughen reprisals against Russia by agreeing to move to a next stage of economic sanctions.
"With sanctions, we are not going to solve the problem," Luxembourg's Jean Asselborn said, stressing that everything must be done to ensure the success of EU-US mediated talks Thursday in Geneva between Russia and Ukraine.
"We must not focus only on sanctions," Asselborn said.
Dutch Foreign Minister Frans Timmermans said it was "too early" to discuss fresh sanctions but warned that the EU had to be prepared to take the next step if Russia showed no sign of backing off.
In eastern Ukraine meanwhile, pro-Kremlin militias continued in control of many government buildings in defiance of a Kiev ultimatum to leave or face the consequences.