KYIV, Ukraine (AP) – Russian troops have left the heavily contaminated Chernobyl nuclear site. Ukrainian authorities say the soldiers departed early Friday after returning control to Ukraine. Meanwhile, eastern parts of the country braced for renewed attacks and Russians blocked another aid mission to the besieged port city of Mariupol. The governor of the Russian border region of Belgorod accused Ukraine of flying helicopter gunships into Russian territory and striking an oil depot Friday morning. The depot is run by Russian energy giant Roseneft about 21 miles from the border. The governor says it was set ablaze by the attack that left two people injured. If confirmed, it would be the first attack of its kind by Ukrainian forces inside Russia.