U.S. Secretary of State John Kerry told his Russian counterpart Monday that Washington was watching events in eastern Ukraine closely and any moves by Moscow to further destabilize Ukraine would "incur further costs for Russia," the State Department said. Spokeswoman Jen Psaki said Kerry also agreed to meet in the next 10 days with top diplomats from Russia, Ukraine, and the European Union in a new effort to calm tensions in eastern Ukraine, where armed pro-Russian groups seized public buildings in three cities overnight. In a telephone call with Russian Foreign Minister Sergei Lavrov, the top U.S. diplomat "called on Russia to publicly disavow the activities of separatists, saboteurs, and provocateurs, called for de-escalation and dialogue, and called on all parties to refrain from agitation in Ukraine," Psaki told reporters. Kerry noted that the actions in eastern Ukraine "do not appear to be a spontaneous set of events," and he referred to "the recent arrests of Russian intelligence operatives working in Ukraine," the Psaki said. "He made clear that any further Russian efforts to destabilize Ukraine will incur further costs for Russia."