Ukrainian troops stand atop of a vehicle as they leave the scene of fighting in Mariupol, eastern Ukraine, Friday, June 13, 2014. Ukraine’s interior minister says that government troops have attacked pro-Russian separatists in the southern port of Mariupol. Arsen Avakov said Friday that four government troops were wounded as forces retook buildings occupied by the rebels in the center of the town.Evgeniy Maloletka / AP
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Moscow sent a “note of protest to Ukraine,” said the Russian Foreign Ministry, which called Ukraine's actions a “gross violation of fundamental rules of international law” and “an illegal act which will not contribute to a peaceful settlement of the armed conflict in the South-East of Ukraine.”
Russian news agencies reported that the Ukrainian troops fled Rostov, but left one of the vehicles behind because it had broken down.
Directly across the border, Ukrainian government forces reclaimed the port city of Mariupol from pro-Russian separatists after hours of fighting.
"At 10:34 a.m. (3:34 a.m. ET), the Ukrainian flag was raised over City Hall in Mariupol," Interior Minister Arsen Avakov wrote on Facebook. At least five separatists and two servicemen were killed before many of the rebels fled, according to Reuters.
Regaining control of Mariupol is important to the Ukrainian government because it serves as a portal for steel, and Ukraine says Moscow of uses the city as a gateway for armored vehicles.
The newly elected President Petro Poroshenko vowed to intensify defense against the pro-Russian separatists following months of unrest in the region and Russia's annexation of Crimea in March.