The Donbass region is home to giant steel smelters and heavy plants that produce up to a third of Ukraine's industrial output. An armed uprising began there in early April, with Kyiv struggling to respond partially due to fear of provoking an invasion by tens of thousands of Russian troops on the other side of the border.

Ukraine's acting president has said police and security forces are effectively "helpless" against insurgents in the Donetsk and Luhansk regions.

Many Russian-speaking business oligarchs from the Donbass area backed ousted President Viktor Yanukovych and exercise great influence over the region. Rinat Akhmetov, the most powerful of these and Ukraine's richest man, has issued a formal statement saying he remained committed to his investments in the Donbass and to keeping the region as part of Ukraine.

The failed Geneva agreement called on the Kremlin to use its influence to get pro-Russian insurgents to leave the government buildings they have occupied in eastern Ukraine. Those forces have not only balked at leaving the buildings but also stepped up their provocations, including capturing European military observers whom the militants paraded before the media.

Armed pro-Russian rebels have said they were not bound by an international deal ordering them to disarm and leave the public buildings they have occupied for weeks. Click the points on the map above for more information or read about notable locations below: