Quoted from Christian Science Monitor, who also says the trouble hasn't yet caught the attention of Washington:
Though no one knows exactly who stands behind the armed men who are blockading the rail lines and highways along the battle front, everyone names the disgruntled oligarch Igor Kolomoisky as the most likely financial backer. Mr. Kolomoisky has at the hands of President Poroshenko over the past couple of years, including being stripped of his governorship of Dnipropetrovsk region in a battle over control of state energy properties, and more recently seeing his most lucrative property, PrivatBank, Ukraine's largest bank, by the government.
A range of opposition forces, most prominently former prime minister and "Orange Revolution" heroine Yulia Tymoshenko and ex-Georgian president-turned-Ukrainian-loose-cannon , have come out in support of the blockaders.