This is a recurring pro-Kremlin disinformation narrative about the war in Ukraine, attempting to portray it as a civil war provoked by the Ukrainian government.
The Office of the Prosecutor of the International Criminal Court stated that "the information available suggests that the situation within the territory of Crimea and Sevastopol amounts to an international armed conflict between Ukraine and the Russian Federation." This international armed conflict began at the latest on 26 February 2014 when the Russian Federation deployed members of its armed forces to gain control over parts of the Ukrainian territory without the consent of the Ukrainian Government. The European Union stated in July 2014 that "arms and fighters continue flowing into Ukraine from the Russian Federation".
At the NATO Summit in Wales in September 2014, NATO leaders condemned in the strongest terms Russia’s military intervention in Ukraine and demanded Russia to stop and withdraw its forces from Ukraine and from the country’s border. NATO leaders also demanded Russia to comply with international law and its international obligations and responsibilities; end its illegitimate occupation of Crimea; refrain from aggressive actions against Ukraine; halt the flow of weapons, equipment, people and money across the border to the separatists; and stop fomenting tension along and across the Ukrainian border.
According to the US Defence Intelligence Agency (DIA), Russian special forces and troops operated to mobilise, lead, equip, and support separatist militias in the Donbas region of eastern Ukraine from spring 2014 to the present, although their presence was denied by Moscow.
Russian President Vladimir Putin admitted Russia's military presence in Ukraine in 2015.