Hope for a rumored truce was shattered Thursday in this strategic eastern port as Russian troops attacked Ukrainian positions near the city with heavy artillery and missile fire, a Ukrainian militia leader said.
"It is a totally new game," said Oleg Odnorozhenko, deputy commander of the volunteer Azov Battalion, adding that the city's fighters are now certain they are being attacked by regular Russian army troops, not just mercenaries and homegrown separatists.
The barrage on the outskirts of Mariupol coincided with declarations by Ukrainian President Petro Poroshenko and leaders of the separatist militants in the country's east that a cease-fire was in the offing at negotiations Friday in Minsk, the capital of Belarus.
But both sides made it clear that a halt in the conflict was contingent on the other side in effect capitulating. That's a condition the resurgent separatists are under no pressure to meet, and retreat would be politically devastating for Poroshenko after the loss of more than 2,600 lives in the fighting since April.
Though authorities in Kiev, the Ukrainian capital, have refused to negotiate with the separatists, whom they have branded as terrorist stooges of the Kremlin, the meeting in Minsk brings together representatives of the government and the separatists, Russia's ambassador to Ukraine and veteran diplomats of the Organization for Security and Cooperation in Europe. The OSCE is the only international security forum of which both Russia and Ukraine are members.
"Tomorrow in Minsk a document will be signed providing for the gradual introduction of the Ukrainian peace plan," Poroshenko told reporters on the sidelines of a NATO summit in Wales, where leaders of the Western military alliance expressed solidarity with his fight to keep Ukraine intact.
NATO Secretary-General Anders Fogh Rasmussen warned Russia against continuing to support the separatists.
"We are still witnessing, unfortunately, Russian involvement in destabilizing the situation in eastern Ukraine," he said. "So we continue to call on Russia to pull back its troops from Ukrainian borders, stop the flow of weapons and fighters into Ukraine, stop the support for armed militants in Ukraine and engage in a constructive political process."
Expectation of a truce being brokered in Minsk was raised a day earlier by Russian President Vladimir Putin's proposed seven-point peace plan, starting with the withdrawal of Ukrainian government troops from the two eastern regions seized by the separatists in April.
Poroshenko's own formula for ending the conflict, which he unveiled during his June 7 inauguration speech, requires that the separatists lay down their arms and relinquish seized territory in exchange for negotiations on more autonomy for their regions within Ukraine.
Putin has denied that Russian troops or armor are engaged in the conflict, an assertion undermined by satellite images released by NATO last week showing columns of Russian tanks and guns crossing the border.
Some of that hardware is now threatening Mariupol in what Kiev authorities suspect is a mission to take control of the entire Sea of Azov coastline, connecting mainland Russia with the Crimean peninsula, which Moscow seized from Ukraine in February and annexed in March.
Odnorozhenko, the Azov Battalion deputy commander, said the Russian columns that pushed across the border about 40 miles to the east last week began striking at Mariupol's perimeter Thursday.
"At first they tried our defenses with a tank raid, and when our firing positions revealed themselves they threw all their artillery at us," the militia commander said, describing the opposing forces as "very thorough and very professional."
The Russian troops and hardware were "poised to encircle the town and force us to leave it to them," Odnorozhenko said. "Their goal is clear: By capturing Mariupol they open the gate for a land route to supply Crimea."
The sounds of battle on the bombarded outskirts failed to dissuade several thousand Mariupol residents from taking part in a rally in the city center against the foreign intrusion.
Demonstrators draped in the blue and yellow of the Ukrainian flag hoisted anti-Putin and antiwar posters. Some read, "Ukraine is a unified country!" and "Mariupol is a Ukrainian city."
"I can't believe a Russian army can come here to conquer us," said Vera Chuyko, a 34-year-old nurse taking part in the rally. "It is like a bad dream. It doesn't make sense. Why destroy our country and kill our people? What for? It is insane!"