Ukrainian forces stop Russian advance towards Sloviansk - presidential aide

FILE PHOTO: Ukrainian sappers arrive in the eastern Ukrainian village of Semenovka, near Sloviansk, July 14, 2014. REUTERS/Gleb Garanich

(Reuters) - Ukrainian troops have held up an advance by Russian forces from the northeastern city of Izyum towards nearby Sloviansk, Oleksiy Arestovych, a Ukrainian presidential advisor said on Wednesday.

"They have focused their forces there, that is where they are trying to advance, but so far they are not succeeding," he said in a video address.