The last few weeks have been bad for the “pro-Russian separatists” in eastern Ukraine. No one took their plebiscite on autonomy seriously, Ukraine’s national elections succeeded in establishing credibility for the central government, and Vladimir Putin has still not come to their rescue. The emboldened Ukrainian government gave the go-ahead to use force in taking back its strategic port city of Mariupol today, and that mission has apparently succeeded:

The Ukrainian flag fluttered over the regional headquarters of Mariupol on Friday after government forces reclaimed the port city from pro-Russian separatists in heavy fighting and said they had regained control of a long stretch of the border with Russia.

The advances are significant victories for the pro-European leadership in a military operation to crush the armed rebellion, which began in east Ukraine in April, and hold the former Soviet republic of 45 million together.

In central Mariupol, police cordoned off several streets, where roadblocks of sandbags and concrete blocks, once manned by rebels, were riddled with bullet-holes and the burnt-out hulk of an armoured personnel carrier with rebel insignia smouldered.

“At 10:34 a.m. the Ukrainian flag was raised over City Hall in Mariupol,” Interior Minister Arsen Avakov wrote on Facebook, less than six hours after the attack began on the city of 500,000, Ukraine’s biggest Azov Sea port.

A ministry aide said the government forces stormed the rebels after they were surrounded and given 10 minutes to surrender. At least five separatists and two servicemen were killed in the battle before many of the rebels fled.

The operation presented the most direct challenge yet to Russia, as it cuts off a key route to Crimea:

Mariupol is the second-largest city in the eastern Donetsk region that has declared independence from the government in Kiev. The key port sits along the main road leading from Russia to the Crimean Peninsula, which Russia annexed in March from Ukraine.

However, rebels in Donetsk claim they have three tanks that crossed the Russian frontier earlier:

The renewed fighting Friday came as rebel leaders confirmed they now have three tanks. Government officials say the tanks were part of a column of armored vehicles that crossed the porous border into Ukraine from Russia, but there has been no independent confirmation that they came from Russia.

Denis Pushilin, a leader of the separatist Donetsk People’s Republic, told Russian state television Friday that they have the tanks but it was “improper to ask” where they had gotten them.

“They are in Donetsk and are the minimum that we have to defend the city,” he said.

Raw video shows that Mariupol was no walkover for Kyiv:

Meanwhile, if the rebels are hoping for help from Putin, they may be disappointed. Putin spoke at length with new Ukrainian president Petro Poroshenko yesterday about how to proceed on a plan for peace, but Poroshenko didn’t feel moved enough by it to postpone the retaking of Mariupol:

On Thursday, Ukrainian President Petro Poroshenko and Russian President Vladimir Putin “held a substantial and long phone conversation,” the Ukrainian President’s media office said. The leaders discussed Poroshenko’s peace plan to resolve the situation in the east of Ukraine, it said. Poroshenko has called on the rebels to lay down their arms and engage in talks.

Also Thursday, Vitaly Churkin, Russia’s U.N. ambassador, said he would introduce a resolution on Ukraine at the U.N. Security Council in light of what he said was a deteriorating situation in the country.

Churkin told reporters the resolution, to be introduced behind closed doors, would focus on stopping the violence in Ukraine and addressing political efforts through the Organization for Security and Cooperation in Europe.

That’s going nowhere in a hurry. The US and UK will almost certainly veto it, if for no other reason than retaliation for Russia’s earlier vetoes of Western proposals at the UN Security Council on Ukraine. Besides, the Putin-backed rebels abducted OCSE observers earlier in the conflict, claiming that they were spies, which makes this proposal look dead on arrival even with Putin’s friends, let alone his opponents.

Now the question will be how Putin will respond to the liberation of Mariupol. At least so far, Moscow’s playing that pretty close to the vest.