(Updates with more quotes, detail)
LONDON, April 8 (Reuters) - Britain said on Tuesday events in eastern Ukraine looked to be part of a Russian strategy to destabilise the country, saying it was "gravely concerned" by pro-Russian protesters' seizure of government buildings.
"There can be no justification for this action, which bears all the hallmarks of a Russian strategy to destabilise Ukraine," British Foreign Secretary William Hague told parliament, saying the seizures looked like part of a plan to damage the credibility of Ukraine's forthcoming presidential election.
"This is something we have to expect in the run-up to Ukrainian presidential elections on the 25th of May," said Hague, saying Russia was trying to make it less credible to hold the presidential ballot in eastern Ukraine and to make it harder for Ukraine "to operate as a democratic state".
Police detained 70 people occupying a regional administration building in eastern Ukraine overnight, but pro-Moscow protesters held out in a standoff in two other cities in what Kiev called a Russian-led plan to dismember the country.
Hague has called on Europe to press ahead with drawing up tough economic sanctions against Russia, saying there has only been a "token" withdrawal of Russian troops from Ukraine's eastern border.
On Tuesday, he said Russia should be aware it would face "far reaching measures, economic and other sanctions" from Europe if it escalated the Ukrainian crisis. "Any invasion of eastern Ukraine of course falls into that category," said Hague. (Reporting by William James and Kylie MacLellan; Editing by Andrew Osborn)