Poland produced a stirring performance in Warsaw to hold Russia to a draw and strengthen their hopes of qualifying for the knockout stages.
The co-hosts came from behind during a thrilling second half, captain Jakub Blaszczykowski scoring the equaliser with a thunderous left-foot shot.
Russia had taken the lead after 37 minutes, when Alan Dzagoev turned in Andrey Arshavin's curling free-kick.
Although both teams had chances to win the game, the spoils were shared.
The result leaves Group A wide open, with all four teams still mathematically able to qualify for the quarter-finals after a night of high drama in the Polish capital.
This was not a rivalry in need of stoking, or a fixture that required additional hype.
And yet fuel was thrown on the fire in the hours before kick-off as riot police clashed with fans from both countries in a series of violent exchanges on the streets of Warsaw.
A march in support of Russia's Independence Day, from the city centre to the stadium, prompted widespread anger among Polish extremists.
If the atmosphere around the stadium was raw at kick-off, the early exchanges were equally frenzied.
Arshavin was immediately in the thick of the action, probing, pressing, jinking beyond defenders. But the best of the early chances fell to Poland.
Ludovic Obraniak's curling free-kick was headed goalwards by Sebastian Boenisch only for Russia goalkeeper Vyacheslav Malafeev to turn the ball away.
Poland had the ball in the net after 17 minutes, but the linesman's flag correctly denied them after Robert Lewandowski and Eugen Polanski had linked up delightfully following an incisive one-touch passing move.
But for all Poland's early exuberance, Russia remained a constant danger. Arshavin and Aleksandr Kerzhakov were at the heart of everything for Dick Advocaat's team, who gradually began to resemble the side that had been imperious in sweeping aside the Czech Republic in their opening game.
Poland struggled to contain the movement of Dzagoev, while Yuri Zhirkov's probing runs down the left flank were equally threatening.
The momentum was shifting and Russia struck decisively.
Arshavin's pin-point free-kick curled menacingly across the penalty area and it was Dzagoev who steered it beyond Poland goalkeeper Przemyslaw Tyton, the ball fortuitously deflecting off his shoulder for his third goal of Euro 2012.
Poland were unbowed, however. They began the second half as they had the first, Polanski finding Lewandowski beyond the final defender but the Borrusia Dortmund striker was driven wide before Malafeev snuffed out the danger with his legs.
Lewandowski was through again moments later but Malafeev was again alert to the danger, punching clear decisively.
The game was becoming increasingly stretched now. Russia threatened every time they broke forward but Poland refused to give up, pouring forward time after time, scattering red shirts and levelling the match with a stunning goal from their captain.
Blaszczykowski escaped the attentions of Zhirkov, cut in from the right flank and unleashed a searing left-foot shot that arrowed beyond Malafeev and into the top left-hand corner of the net. The goal sparked scenes of euphoria in the stadium and Poland clearly drew strength from the partisan support.
Adrian Mierzejewski fired wide from 25 yards as Poland began to sniff an unlikely victory. Lewandowski saw a shot blocked before left-back Sebastian Boenisch surged forward, beat two Russian defenders and thundered a shot over the bar from distance.
Both teams had chances to win the match but at the final whistle it was the Polish supporters whose smiles were widest.