Arsenal were left to rue a moment of carelessness by goalkeeper Jens Lehmann at Ewood Park.

He allowed Blackburn to secure a point when he flapped at a shot from David Dunn and watched in disbelief as it nestled in the net.

It was the second time this season the German has been punished for a lack of concentration. On the opening day of the season he allowed Fulham's David Healy to score from close range.

Arsenal went on to secure a victory against their London neighbours but were not so fortunate in Lancashire after Robin van Persie had given them the lead.

The only sour note for Blackburn was the dismissal of skipper Ryan Nelsen for two yellow cards.

Arsenal took the lead in the 18th minute when Van Persie took advantage of some sloppy defending to score.

Goalkeeper Brad Friedel failed to deal with Eduardo Da Silva's shot after Theo Walcott had headed the ball on.

Nelsen and David Dunn both had chances to clear but failed to do so and Van Persie took advantage his second goal of the season

It was just the start Arsenal wanted after their Champions League victory against Sparta Prague in midweek.

However manager Arsene Wenger was forced to make a change in the 25th minute with William Gallas limping off and being replaced by Philippe Senderos.

Blackburn almost drew level in the 34th minute following a free-kick from David Bentley.

He picked out Christopher Samba at the back post and the towering defender headed the ball back across the area.

Nelsen was the first to react and powered the ball forward only to see his effort come back off the post.

Blackburn, though, were still looking vulnerable at the back and a mistake by Stephen Warnock let in Walcott with Nelsen dragged out of position.

Walcott was in two minds whether to shoot or cross and failed to trouble Friedel in the home goal.

The Arsenal youngster sent a harmless ball across the face of the area and Van Persie was unable to get a touch.

Then Senderos delivered a goal-bound header a minute before the break only to see Samba make the clearance.

Bentley then tried to curl a free-kick beyond Lehmann in the 53rd minute but his effort fail to trouble the goalkeeper.

This was a good spell by Blackburn and Roque Santa Cruz sent a header narrowly wide of the post in the 57th minute following a free-kick from Bentley.

Derbyshire then almost equalised three minutes later when he got on the end of a cross from Bentley but Toure made a vital interception.

There was controversy in the 62nd minute when Cesc Fabregas handled Samba's effort on the line but referee Alan Wiley awarded Arsenal a free-kick for an infringement.

Lehmann had to look lively in the 66th minute to push away an inswinging free-kick driven at pace from Morten Gamst Pedersen.

Then came his howler which allowed Dunn to score his first goal in his second spell for the club.

Blackburn were growing in confidence and Pedersen made space down the left only to find the side-netting with his shot.

However they were reduced to 10 men in the 83rd minute when Nelsen picked up his second yellow card of the game for a challenge on Van Persie.

Blackburn, though, kept their shape to take a point and continue their good start to the season.

Teams

Blackburn Friedel, Emerton, Samba, Nelsen, Warnock, Bentley,Savage, Dunn, Pedersen, Santa Cruz (McCarthy 88),Derbyshire (Ooijer 85).

Subs Not Used: Brown, Kerimoglu, Roberts.

Sent Off: Nelsen (84).

Booked: Bentley, Samba, Savage, Nelsen.

Goals: Dunn 72.

Arsenal Lehmann, Sagna, Toure, Gallas (Senderos 24), Clichy,Walcott (Bendtner 73), Flamini, Fabregas, Hleb,Eduardo (Denilson 65), Van Persie.

Subs Not Used: Almunia, Song Billong.

Booked: Flamini, Eduardo, Clichy, Van Persie.

Goals: Van Persie 18.

Att: 24,917

Ref: Alan Wiley (Staffordshire).