(VOVworld) - Fierce fighting between Ukrainian troops and pro-Russian rebels broke out in the southeastern city of Mariupol on Friday, killing 21 people.

Ukrainian government soldiers aim their weapons as they guard an administration building in Mariupol, eastern Ukraine, Thursday, May 8, 2014 (Photo: AP)

According to Russia’s Interfax news agency, Ukrainian troops used large caliber weapons as they tried to take an occupied government building in the city. Members of a crew from Britain's ITV News in the city said that they saw heavy guns being used and smoke from burning tyres rising above Mariupol.