The U.K. Defense Ministry said in a Sunday morning update that Russian troops are “paying a high price” with each advance in Ukraine because the Ukrainian Armed Forces “continues to offer staunch resistance across the country.”  

The update added that Russian troops are attempting to surround Ukrainian forces in the east of the country by advancing from Kharkiv in the north and Mariupol in the south.

“Russian forces advancing from Crimea are attempting to circumvent Mykolaiv as they look to drive west toward Odesa," the ministry said.

Russian President Vladimir Putin has reportedly placed one of his top intelligence officials under house arrest, a move that one expert tells Fox News Digital would be a sign that Putin is seeking to shift blame for a Ukrainian invasion that U.S. intelligence believes has not gone according to plan.

Russian journalist Andrei Soldatov claims Putin has arrested Sergey Beseda, head of the Federal Security Service, The Sunday Times of London reported.

Fox News has not independently confirmed the report.

Beseda has reportedly been placed under house arrest along with his deputy Anatoly Bolyukh.

The Federal Security Service (FSB) is Russia’s top security and counterintelligence apparatus. One former U.S. intelligence officer tells Fox News Digital that the move signals Putin’s dissatisfaction with his intelligence community’s assessment of the Ukrainian invasion.

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A former U.S. intelligence official tells Fox News Digital that Russia has embraced over the years a similar plan to an American military concept known as the OODA loop which enables one side to react to unfolding events more rapidly and efficiently than an opponent. 

The OODA loop, which stands for observe, orient, decide, act and was developed by U.S. Air Force Col. John Boyd and is defined by Tech-Target as a "four-step approach to decision-making that focuses on filtering available information, putting it in context and quickly making the most appropriate decision while also understanding that changes can be made as more data becomes available."

The strategy is especially useful, according to Tech-Target, in "scenarios where competition is involved and where the ability to react to changing circumstances faster than an opponent leads to an advantage."

Rebekah Koffler, a former U.S. Defense Intelligence Agency agent and author of "Putin's Playbook: Russia's Secret Plan to Defeat America," told Fox News Digital that the Russians have adopted a similar concept.

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Click here to read Fox News' live coverage from Saturday.