Dundee United recorded their second derby win of the season over Dundee with a convincing victory at Dens Park.
Keith Watson dived to head home Barry Douglas's corner before Dundee's Steven Milne volleyed over from close-range.
The home side were denied a second-half penalty after Brian McLean's handball.
An innocuous foul on Stuart Armstrong led referee Willie Collum to award United a controversial spot-kick that John Daly scored, then Willo Flood added a deflected third.
Dundee made their intentions clear by applying some early pressure originating from good wing-play on both sides.
Steven Milne released Nicky Riley down the right-hand side and he got the better of Barry Douglas to cause the first fluster in the visitors' box before Flood cleared.
Almost immediately after, Jim McAlister showed his capabilities down the left, skilfully knocking the ball past Keith Watson and crossing for Milne, but Gavin Gunning got there first to clear.
From the resultant corner, Riley had Radoslaw Cierzniak in the United goal worried for a second with a high looping header from the edge of the box that landed on the roof of the net.
It took until the 15-minute mark for United to apply any sort of real pressure.
Flood turned inside Kevin McBride before dinking a cross into the box, but Milne headed away. The header fell to Stuart Armstrong, whose 20-yard effort was deflected for a corner.
From that set-piece, United took the lead on 17 minutes.
Douglas clipped the ball left-footed to the near-post and Watson darted to connect with a diving header that had enough power to negotiate its way past three Dundee defenders on the line.
It was definitely against the run of play, but United were not caring about that.
A few minutes later, the first yellow card of the afternoon went to the Tangerines' left-back, Douglas, after a blatant trip on Riley as he cut inside on the right.
The home fans were on their feet in the 26th minute when McAlister's high flicked pass found John Baird. The forward met it with a header, but Cierzniak saved before realising the offside flag had been raised.
Shortly after, Dundee had a fantastic chance to equalise.
Matt Lockwood's whipped cross found the head of McAlister, who nodded to Milne, but he volleyed left-footed over the bar from eight yards out when he should have hit the net.
Rab Douglas's hands were warmed by another stinging Watson effort from long-range, then a terrific cross by Douglas attacking on the left led to Johnny Russell heading narrowly wide.
Russell looked lively again on 36 minutes, scurrying through the middle of the park towards goal as he shrugged off challenges. Eventually, he met the onrushing Douglas just inside the box and the ball was cleared.
Armstrong ensured the second half got off to a frenetic start by latching on to Russell's reverse pass to shoot low, but Douglas was equal to it.
Immediately after, there was a huge penalty claim from Dundee.
Baird's cross clearly hit the lower arm of Brian McLean and the home fans were astonished that referee Willie Collum did not award a spot-kick.
On 50 minutes, livewire Russell smacked the post after capitalising on a dreadful clearance by Declan Gallagher.
After the hour-mark, Dundee again pushed for the equaliser.
Iain Davidson's fizzed shot wide did not trouble Cierzniak, but Lockwood's 25-yard free-kick on 68 minutes certainly did, as the Polish keeper dived to his top-right corner to save.
Referee Collum then caused a stir by awarding United a penalty on 71 minutes.
Daly's shot was smothered by Rab Douglas, but Collum felt Armstrong had been fouled by Gary Irvine while crossing that Daly chance.
The striker himself stepped up to convert convincingly into Douglas's left corner, making it 2-0.
Despite Dundee trying to revive the game, United killed it off.
Flood's shot from the edge of the box was deflected off Kyle Benedictus, Douglas touched it on to the post, but it came back and hit the goalkeeper again and rolled into the net.
Full Time The game is over, as the referee blows his whistle.
Unfair challenge on Gary Irvine by Michael Gardyne results in a free kick. Gary Irvine takes the direct free kick.
Kevin McBride takes a shot. Save by Radoslaw Cierzniak.
Stuart Armstrong provided the assist for the goal.
87:11 Goal scored
Goal! - Willo Flood - Dundee 0 - 3 Dundee U Willo Flood finds the net with a goal from inside the penalty area low into the middle of the goal. Dundee 0-3 Dundee Utd.
Gavin Gunning takes the direct free kick.
Booking Booking for Iain Davidson for unsporting behaviour.
Iain Davidson gives away a free kick for an unfair challenge on Richie Ryan.
A cross is delivered by James McAlister, save by Radoslaw Cierzniak.
Corner from the right by-line taken by James McAlister, clearance made by Jon Daly.
Free kick awarded for a foul by Iain Davidson on Radoslaw Cierzniak. Radoslaw Cierzniak restarts play with the free kick.
Substitution (Dundee) makes a substitution, with Martin Boyle coming on for Steven Milne.
The ball is delivered by Matthew Lockwood, Radoslaw Cierzniak makes a save.
Free kick awarded for a foul by Brian McLean on John Baird. Kevin McBride takes the direct free kick.
The ball is delivered by James McAlister, clearance made by Gavin Gunning.
Corner taken right-footed by James McAlister, Brian McLean manages to make a clearance.
James McAlister takes a outswinging corner.
Jon Daly fouled by Kyle Benedictus, the ref awards a free kick. Direct free kick taken by Barry Douglas.
Unfair challenge on Stuart Armstrong by Kevin McBride results in a free kick. Barry Douglas crosses the ball from the free kick left-footed from right channel. Free kick awarded for a foul by Jon Daly on Declan Gallagher. Rab Douglas takes the free kick.
Johnny Russell produces a shot from just outside the penalty box that bounces off the post.
Effort on goal by Willo Flood from outside the box goes harmlessly over the bar.
The offside flag is raised against Johnny Russell. Rab Douglas takes the free kick.
The ball is swung over by John Baird, save by Radoslaw Cierzniak.
Stuart Armstrong takes a shot. Save made by Rab Douglas.
The referee gets the second half started.
45:00 +1:11 Half time
Half Time The whistle is blown to end the first half.
The assistant referee flags for offside against Rudi Skacel. Rab Douglas takes the free kick.
Effort on goal by John Baird from just outside the area goes harmlessly over the target.
Free kick awarded for an unfair challenge on Kevin McBride by Stuart Armstrong. Gary Irvine takes the free kick.
Foul by Declan Gallagher on Johnny Russell, free kick awarded. Barry Douglas restarts play with the free kick.
The ball is sent over by James McAlister, Steven Milne takes a shot. Save made by Radoslaw Cierzniak.
Declan Gallagher concedes a free kick for a foul on Barry Douglas. Radoslaw Cierzniak takes the indirect free kick.
Free kick awarded for a foul by Stuart Armstrong on Gary Irvine. Gary Irvine takes the free kick.
The ball is crossed by Keith Watson.
Keith Watson takes a shot. Brilliant save by Rab Douglas. Outswinging corner taken from the left by-line by Barry Douglas. Header from close in by Johnny Russell misses to the right of the target.
The offside flag is raised against Steven Milne. Free kick taken by Radoslaw Cierzniak.
The ball is swung over by Keith Watson, Rudi Skacel takes a shot. Rab Douglas makes a comfortable save.
Corner taken by James McAlister from the right by-line played to the near post, Brian McLean makes a clearance.
Jon Daly concedes a free kick for a foul on Declan Gallagher. Free kick taken by Matthew Lockwood.
Gavin Gunning delivers the ball, comfortable save by Rab Douglas.
Inswinging corner taken by Willo Flood, Steven Milne manages to make a clearance.
The ball is sent over by James McAlister. The assistant referee flags for offside against Steven Milne. Indirect free kick taken by Radoslaw Cierzniak.
Willo Flood challenges Nicky Riley unfairly and gives away a free kick. Free kick crossed left-footed by Matthew Lockwood, Barry Douglas manages to make a clearance.
Jon Daly is ruled offside. Rab Douglas takes the free kick.
John Baird is flagged offside by the assistant referee. Free kick taken by Radoslaw Cierzniak.
Jon Daly concedes a free kick for a foul on Kyle Benedictus. Rab Douglas restarts play with the free kick.
James McAlister challenges Keith Watson unfairly and gives away a free kick. The free kick is swung in left-footed by Barry Douglas, Matthew Lockwood manages to make a clearance.
Kevin McBride concedes a free kick for a foul on Stuart Armstrong. Stuart Armstrong takes the direct free kick.
Corner taken right-footed by Willo Flood to the near post, Gary Irvine makes a clearance.
Free kick awarded for an unfair challenge on Rudi Skacel by Iain Davidson. The free kick is delivered left-footed by Barry Douglas from left channel, Kyle Benedictus makes a clearance.
Matthew Lockwood crosses the ball in from the free kick, Willo Flood makes a clearance.
Booking Barry Douglas receives a yellow card.
Barry Douglas challenges Nicky Riley unfairly and gives away a free kick.
Foul by Stuart Armstrong on Iain Davidson, free kick awarded. Matthew Lockwood takes the free kick.
Assist on the goal came from Barry Douglas.
16:15 Goal scored
Goal! - Keith Watson - Dundee 0 - 1 Dundee U Keith Watson grabs a headed goal from close in. Dundee 0-1 Dundee Utd.
Outswinging corner taken by Barry Douglas from the left by-line,
Keith Watson sends in a cross, blocked by James McAlister. Outswinging corner taken right-footed by Willo Flood, Steven Milne manages to make a clearance.
Rudi Skacel gives away a free kick for an unfair challenge on James McAlister. Direct free kick taken by Matthew Lockwood.
Nicky Riley is caught offside. Radoslaw Cierzniak takes the indirect free kick.
Nicky Riley takes has a header from just inside the penalty box which clears the crossbar.
Inswinging corner taken by James McAlister from the left by-line, save by Radoslaw Cierzniak.
Corner taken right-footed by James McAlister to the near post, Stuart Armstrong manages to make a clearance.
The ball is delivered by James McAlister, Gavin Gunning makes a clearance.
The ball is sent over by Stuart Armstrong, Kyle Benedictus makes a clearance.
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