Robin van Persie scored an injury-time winner to give Manchester United a 3-2 win over Manchester City on Sunday, ending the defending champion's unbeaten start to the Premier League season and taking his side six points clear atop the standings.
"We were in control, but City always come back," Van Persie said. "It's a really special way to end this game, with the three points (won) in a really dramatic way. ... To go six points clear, to beat our closest rivals, we're delighted. We're going to celebrate."
In the frenzy following the goal, United defender Rio Ferdinand was hit by an object thrown from the stands, leaving him bleeding from a cut above his left eye, and Hart was confronted on the pitch by a fan.
City said the club will assist the police with its investigation into "the throwing of missiles" and trouble between both sets of fans.
"Manchester City wishes to offer its sincere apologies to Rio Ferdinand," City said in a statement. "The club unreservedly condemns the actions which led to his being injured."
Wayne Rooney had set United on the way to avenging last season's double derby defeat to City by scoring twice in the first half against the run of play to take his career league tally to 150 goals.
But Van Persie, who Arsenal claimed had been made an offer by City in the offseason, struck the late blow that ended the hosts' unbeaten league home run -- stretching back to December 2010.
"Today was a special one simply because they haven't lost at home for two years, both of us are contending at the top of the league," United manager Alex Ferguson said. "It was a fantastic game, you couldn't take your eyes off that."
The loss made City's week even worse, with Roberto Mancini's having finished last in its Champions League group and missed out on the knockout stage for a second successive season.
Tensions had been high from the start in the Manchester derby between the league's top two teams.
Rooney was fortunate not to be booked in the opening minutes for fouls on David Silva and Yaya Toure.
Balotelli squandered another good opening when he sliced the ball over from Clichy's cutback.
But Hart's first action was to pick the ball out of his own goal when Rooney put United in front after a lightening counterattack that saw 10 touches in 15 seconds.
After De Gea threw the ball out, Ashley Young headed on to Robin van Persie and a chest-down released the winger down the left flank.
Young slotted the ball through to Rooney, whose mishit shot bobbled through Gareth Barry's legs into the net.
City continued to dominate but couldn't make it count, with Sergio Aguero failing to trouble De Gea with a low shot.
But Rooney was on target again, after ghosting into the penalty area.
Winger Antonio Valencia and Rafael Da Silva combined down the right flank before the defender picked out Rooney, who evaded Kolo Toure to take his derby tally to 10 goals, overtaking Bobby Charlton's United record.
Mancini was getting increasingly anxious on the touchline bellowing out instructions to his players, clearly unhappy at the defensive frailties.
The closest City came to reducing the deficit was Barry's strike that went wide.
When Balotelli gave the ball away after the break, Mancini immediately told Tevez to start warming up. The Argentina striker came on just seven minutes into the second half, and Balotelli stormed down the tunnel.
United had the ball in the net again on the hour, but Young was ruled to be offside when he pounced on the loose ball after Van Persie struck the post.
"Football can kick you in the teeth that way," Ferguson said.
City immediately went up the other end and scored.
De Gea pulled off a double save, first denying Tevez and then Aguero from the rebound. But the United defense didn't close down Tevez, who squared to Toure to score on the hour.
Silva was denied an equalizer by De Gea saving with his left shoulder and the ball then came off the crossbar.
After substitute Edin Dzeko helped City secure a corner, Van Persie's headed clearance went straight to Yaya Toure, who slotted the equalizer into the net.
"At that moment in time they deserved that," Ferguson said. "They came back, were fighting like hell, they gambled everything on the three strikers. But up to that point I thought we were far better than them."
And United got the winner after Rafael Da Silva was fouled by Carlos Tevez, setting up the free kick for Van Persie.
"It got a little deflection, but it was a tremendous hit," Ferguson said. "He's kept them on the back foot the whole time."
Information from Press Association and The Associated Press was used in this report.