Four Ukrainian soldiers were killed and 30 others injured in clashes in the Eastern Ukrainian city of Slavyansk on Monday, Interfas news agency said, citing Ukrainian Interior Ministry sources. The fatalities and casualties took place during fierce clashes in the Slavyansk, they added. The sources said Ukrainian jet fighters bombarded pro-Russian gunmen who were demanding the establishment of federal system in Ukraine. Russia media have reported that more than 80 people were killed since military operations began in eastern Ukraine. Meanwhile, Itar-tass news agency said Foreign Minister Sergei Lavrov had arrived in Vienna to participate in the Council of Europe meeting