From the end of February 2014, demonstrations by pro-Russian and anti-government groups took place in major cities across the eastern and southern regions of Ukraine, in the aftermath of the Euromaidan movement and the 2014 Ukrainian revolution. During the first stage of the unrest, Crimea was annexed by the Russian Federation after a crisis in the region, Russian military intervention, and an internationally criticized referendum. Protests in Donetsk and Luhansk oblasts escalated into an armed separatist insurgency. This led the Ukrainian government to launch a military counter-offensive against the insurgents, which resulted in the ongoing War in Donbass. From late 2014, cities outside of the Donbass combat zone, such as Kharkiv, Odessa, Kiev and Mariupol, were struck by bombings that targeted pro-Ukrainian unity organizations.