An attack on the city of Novoazovsk by pro-Russian troops and military equipment has opened a third front, after fighting in the cities of Luhansk and Donetsk, and near the southern city of Mariupol. Ukrainian troops retreated from the city as shelling continued. The retreat verified Western and Ukrainian claims Russia was leading a counteroffensive after Ukrainian troops advanced in Luhansk and Donetsk.
The Obama administration said Tuesday Russia sent tanks, artillery and infantry over the border between Russia and Ukraine, and the U.S. ambassador to Ukraine noted "a Russian-directed counteroffensive may be underway."
Western officials speculated Russia may be attempting to open a corridor to Donetsk from the border, and possibly seize a sea outlet in the event it attempts to establish a breakaway enclave in eastern Ukraine. Some suggest it is an attempt to link the pro-Russian provinces of Ukraine with Crimea, the strategic peninsula taken by Russia and annexed in March.
Russia claims Ukrainian separatists are fighting with captured Ukrainian military equipment and has denied intervening. However, Western officials are convinced the military material present in Ukraine is from Russia, noting Ukraine's Krasnodon region contains artillery but the Ukrainian army has not penetrated that far, and the separatists are not qualified to use the weaponry.
The invasion comes after an inconclusive, one-day summit meeting between Russian President Vladimir Putin and Ukrainian President Petro Poroshenko in Minsk, Belarus.