U.S. Secretary of State John Kerry is calling for Russian support "without preconditions" for efforts to free European monitors seized Friday by pro-Russian gunmen in eastern Ukraine.
A senior State Department official said Kerry delivered his demand Saturday in a telephone call to Russian counterpart Sergei Lavrov. In a statement, Moscow later said it is taking what it called "all measures to resolve the situation," but blamed Ukrainian authorities for failing to secure the safety of the team.
Near the eastern city of Slovyansk, separatists on Friday seized a bus carrying more than a dozen people from the Vienna-based Organization for Security and Cooperation in Europe .
The German-led monitoring team was acting under the authority of a four-party agreement directing the OSCE to monitor security and human rights in Ukraine's Russian-speaking east and south. The deal, reached in Geneva, was signed by Russia, Ukraine, the United States and the European Union.
Separately, interim Ukrainian Prime Minister Arseniy Yatsenyuk told reporters Saturday that Russian aircraft had violated Ukrainian airspace seven times overnight.
"We do understand the reason Russian military did it. The only reason is to provoke Ukraine to strike missile and to accuse Ukraine of waging the war to Russia."
U.S. military officials on Friday also said Russian aircraft had overflown Ukrainian airspace.
For its part, the Russian Defense Ministry, in a statement Saturday, said its "objective monitoring of the air situation" had not detected any overflight violations.
Meanwhile, in the eastern Ukrainian city of Donetsk, VOA correspondent Brian Padden says he was confronted by an angry mob Saturday, as he tried to cover a rally in front of an occupied building. He says protesters accused him of supporting a "fascist" U.S. government.
"As we were walking away, the crowd just got more angry and started following us and one guy tried to grab my colleague's camera. I tried to stop him. Then he grabbed me and another guy came with a baton. But, before anything could really deteriorate into a real scuffle, the police kind of came between all of us and pulled us out and we just kept walking. But, they followed us for a good 20 meters, continuing to yell at us to 'get out,' to 'go home.' "
Armed, pro-Russian gunmen have seized government facilities in about 10 cities in eastern and southern Ukraine, and are demanding a referendum on whether to secede from the country and join Russia.
In a joint statement late Friday, the Group of Seven major economies announced it had agreed to "move swiftly" on new sanctions against Russia because of its alleged interference in Ukraine.
The G-7 nations said they would take measures to intensify "targeted sanctions" against Moscow. A U.S. official said the penalties could take effect as early as Monday.