The United States has warned Russia about heightened tension in eastern Ukraine after pro-Russian demonstrators seized government buildings in three cities.
In a telephonic conversation, Secretary of State John Kerry told Russian counterpart Sergei Lavrov said that any Russian efforts at destabilisation 'would incur costs'.
According to the BBC, they also discussed the possibility of direct talks within the next 10 days.
Ukraine is sending security officials to Donetsk, Luhansk and Kharkiv, after buildings there were stormed.
US State Department spokeswoman Jen Psaki said that in the telephone call, Kerry 'called on Russia to publicly disavow the activities of separatists, saboteurs and provocateurs' in Ukraine, the report said.
The US and the EU have already imposed targeted sanctions on Russian and Ukrainian individuals over the annexation of Crimea.
According to the report, pro-Russian protesters seized official buildings in Kharkiv, Luhansk and Donetsk on Sunday night.
Ukraine's interim President Oleksandr called the unrest an attempt by Russia to 'dismember' Ukraine.
Speaking on national TV, Turchynov, who has cancelled a visit to Lithuania to deal with the worsening crisis, said it was 'the second wave' of a Russian operation to destabilise Ukraine, overthrow the government and disrupt planned elections, the report added.