Britain summoned Russia's ambassador to clarify reports of a Russian military incursion into Ukraine and a build-up of equipment near the border, the Foreign Office said.
Russian ambassador Alexander Yakovenko was summoned following reports that a small column of Russian armoured vehicles had crossed overnight into an area of Ukraine where pro-Moscow rebels are battling government forces.
Nato has accused the Kremlin of escalating the conflict in Ukraine.
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Scotland Yard said the male youths will appear in custody at Westminster Magistrates' Court on Saturday.
Windy this weekend with gales across northwestern parts of the UK. Rain spreading southeast.
Greater Manchester Police said "inquiries are ongoing to fully understand the circumstances of the incident."