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Kiev, Ukraine (CNN) - "Russia has launched large-scale incursions into Ukraine," a British government source said Friday, moving between 4,000 to 5,000 troops into its western neighbor's territory, with some 20,000 more perched on the border.
The statement comes despite Moscow's fervent claims its forces aren't in Ukraine, and significantly more than a U.S. official's earlier claim of 1,000 Russian troops.
The British source said the Russian troops are aligned in "formed units" and taking part in fighting around Luhansk and Donetsk.