Ukrainian security forces have regained control of Mariupol, a port city in the Donetsk region that has changed hands several times.
Interior Minister Arsen Avakov says Ukrainian forces raised the country’s flag over city hall on Friday.
Earlier in the day, he said security forces had surrounded the rebel-held city.
Pro-Russian separatists in Mariupol said five members of their group had been killed in fighting.
On Thursday, pro-Russian separatists in the city of Donetsk said a van used by separatist rebel leader Denis Pushilin exploded in the central city, wounding at least three bodyguards.
Rebels said Pushilin — one of the leaders of the self-proclaimed Donetsk People’s Republic — was not in the vehicle when the blast occurred in front of a separatist-occupied building.
Also On Thursday, Ukrainian Interior Minister Arsen Avakov accused Russia of allowing an armored column, including three military tanks, to cross into Ukraine at a border control point manned by separatists.
A spokesman for President Petro Poroshenko said the Ukrainian leader told Russian President Vladimir Putin the reported crossing was “unacceptable.” The spokesman said the two leaders spoke by phone.
A Kremlin statement said Poroshenko briefed Putin on plans to settle unrest in the southeast of Ukraine. The statement said the two men also discussed bilateral relations.
It was not immediately clear whether Russian troops crossed into Ukraine with the tanks or whether the column was under rebel control.
Russia, which annexed Ukraine’s Crimea peninsula in March, has repeatedly said it would not make further intrusions into Ukrainian territory.
In another development, Russian forces began military exercises Thursday in the Baltic Sea enclave of Kaliningrad. Moscow says the exercises are a response to ongoing NATO maneuvers in European NATO countries near its borders. Kaliningrad is a tiny Russian territory wedged between NATO member-states Lithuania and Poland.
In Moscow, meanwhile, Putin marked one of Russia’s main holidays, Russia Day, with praise for the annexation of Crimea. In an address, Putin said the peninsula and its strategic Black Sea port of Sevastopol have come back to their “homeland.” He called the annexation a “historic reunification” and said it took place peacefully “and fully in line with the norms of international law.”
Western governments and the United Nations say the peninsula has been occupied by Russian soldiers.