As the U.S. moved Thursday to cut American exports to three Russian airlines and the U.N. General Assembly voted to suspend Russia from the United Nation's Human Rights Council, U.K. officials warned that Russian shelling in Ukraine was a prelude to a greater assault. 

Britain's defense ministry says the country is targeting infrastructure to wear down Ukraine's government and military ahead of a renewed attack. 

In an intelligence update on Thursday, the ministry said that "progressing offensive operations in eastern Ukraine is the main focus of Russian military forces."

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Russia, they continued, appears to be targeting the "line of control" between areas in Donbas controlled by Ukraine and those held by Russia-supporting separatists.

The U.K. said, "Russian forces are likely to continue facing morale issues and shortages of supplies and personnel."

The Russians have largely withdrawn around the capital city of Kyiv and northern Ukraine. 

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This warning comes as Ukraine has told residents to leave impacted areas and urged Western nations aiding their defense to send "weapons, weapons and weapons."

"The more weapons we get and the sooner they arrive in Ukraine, the more human lives will be saved," Ukrainian Foreign Minister Dmytro Kuleba said at NATO headquarters. 

NATO Secretary-General Jen Stoltenberg has called on countries belonging to the Western alliance to send Ukraine more weapons. 

While countries have provided Ukraine with portable anti-tank and anti-aircraft weapons, they have been reluctant to supply aircraft, tanks or any equipment that Ukrainian troops would have to be trained to use.

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On Wednesday, members of the House of Representatives passed legislation calling for a federal government report on evidence of war crimes committed during the war.

The U.S. also announced sanctions against Russian President Vladimir Putin’s two adult daughters and said it is toughening penalties against Russian banks. 

Britain banned investment in Russia, committing to end its dependence on Russian coal and oil by the end of the year.

Russian Foreign Minister Sergey Lavrov on Thursday accused Ukraine of backtracking on proposals it had made over Crimea and Ukraine’s military status and said Washington and its allies had pushed Ukraine to keep fighting. 

Lavrov said Russia intended to continue talks with Ukraine and the Kremlin said it would make a decision on whether Putin will take place in a G20 summit later this year based on how events evolve.

The Kremlin continues to insist its troops have committed no war crimes and that Ukrainians have staged images of streets lined with hundreds of bodies.

Ukrainian President Volodymyr Zelenskyy said Russian forces had removed dead bodies in an attempt to cover up war crimes in areas still under their control.

"This is only an attempt to hide the evidence and nothing more," he said.

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The International Criminal Court opened an investigation into possible war crimes in Ukraine before the grim discoveries.

The Associated Press contributed to this report.