Ankergren was at the centre of controversy after a cigarette was thrown at him in the aftermath of Millwall scoring.
Mounted police were needed to keep control as dozens of Lions fans invaded the pitch after Neil Harris' winner in yesterday's League One play-off semi-final first leg at the New Den.
Ankergren said: "There is no place for this in football. Millwall must be punished."
Six fans have been identified and banned for life and a Scotland Yard spokesman added: "One man was arrested on suspicion of assault."
Leeds manager Simon Grayson tried to play down the incident ahead of Thursday's return leg at Elland Road.
He said: "You know that in play-off semi-finals the atmosphere is quite hostile and people get exuberant.
"The authorities handled it well. Our players didn't respond to anything. I'm just here to protect my players. They're all OK and nothing much was made of it.
"Casper hasn't mentioned it to me. Anyway, I wouldn't want to take Casper on if I were a Millwall fan."
Dane Ankergren, 6ft 3in, felt Millwall should be punished for the behaviour of some of their fans.

Ankergren said: "There was something thrown at me. I didn't see what it was as I turned my back on it. I was pushed in the back by one of the fans that came on the pitch, too. It should never happen - fans should not be allowed on to the pitch.
"I'm not sure what the security were doing as no one came to remove them. They are meant to be here to protect the players. It's not good enough.
"Anything could have happened. Luckily it didn't and hopefully I wouldn't experience that again. English fans are normally much better than Danish fans, who always throw stuff on the pitch and at players.
"But it has happened here at Millwall and I hope something will be done. It is a disgrace to football. It's very bad for football and Millwall should be punished."
Police had anticipated trouble and had limited Leeds to about 1,000 fans while Millwall were allowed to admit only members.
Defender Sam Sodje showed the Leeds spirit as he battled on after dislocating a shoulder. Sodje was the rock in defence as the Lions threatened to extend their lead.
Big Sam, who went into the game carrying a knee injury, looked as though he had tweaked a hamstring in the first half and then went down with a dislocated shoulder in the second. He landed in a heap after he and two other players went up for a cross.
Boss Grayson said: "Sodje dislocated his shoulder and put it back himself. He has been struggling with a knee injury all season and he seemed to have damaged himself in the first half but he never complains and just carries on."
Sodje needed to for he did not get the support he might have expected, especially from the League One player-of-the-year Jermaine Beckford.

Striker Beckford rarely looked like adding to his haul of 34 goals for the season after having an early shot saved by keeper David Forde.
Beckford found the attentions of Zak Whitbread and skipper Tony Craig too intimidating after a skirmish at Elland Road early in the season which led to a three-match ban for the striker for an elbow on Forde.
Fabian Delph, put out wide on the left, also failed to get into the game - other than when he brought down Gary Alexander with a desperate, needless tackle which was fortunate to bring only a yellow card rather than a red which would have put him out of the second leg.
But Leeds went to London clearly determined to defend and take back a goalless draw to Elland Road on Thursday.
But they came undone in the 71st minute when the outstanding Jimmy Abdou played a perfect long ball over the top to the feet of Alexander.
His cross was missed by Leeds skipper Richard Naylor, allowing substitute Harris to rifle home with a right-foot shot.
Grayson was full of sympathy for his captain. He said: "He hasn't put a foot wrong all season and he slipped when the cross came in."
Leeds, who know there is scarcely a piece of tissue paper between these teams after three matches this season, will have to raise their game if they are to break their jinx and gain promotion to the Championship.
Certainly Millwall have broken their duck, winning their first play-off game in nine attempts.
It would be a brave man who bet on the result of the second leg and who would take their place at Wembley.
This article has 7 comments
I was at the game no trouble what so ever just a few over excited kids on the pitch when Harris scored and no mention of Akergren spitting at the fan on the pitch before anything happened
and Akergren also spat at some young kids
get your facts right before you go to print or else go to spec savers
By lions fan. Posted May 11 2009 at 10:32 AM.
I was at the game no trouble what so ever just a few over excited kids on the pitch when Harris scored and no mention of Akergren spitting at the fan on the pitch before anything happened
and Akergren also spat at some young kids
get your facts right before you go to print or else go to spec savers
By lions fan. Posted May 11 2009 at 10:30 AM.
This is scandalous!!!!!!!
if this were a LEEDS fan leeds would have been booted out of the play-offs alltogether!!
Leeds have had enough to deal with over recent years with point deductions and such and i feel if it were a leeds fan we would have been severly punished!!!!!!
GET MILLWALL OUT!!!!!!
Leeds will win at elland road on thursday anyway!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
By jason bastow. Posted May 10 2009 at 5:04 PM.
I was at the game and yes a few fans did invade the pitch when Harris scored as fans often do with excitment. A few games comes to mind where fans invade...Wolves final game where they won promotion and also a couple of the playoff games around the country but they're not made out to be thugs just excited fans! I will agree there were a couple of idiots who were quickly removed by security! I took photos around the ground during the game and there were no signs of any trouble just celebrations even the players and the manager did a whole circuit at the end of the game and we all cheered so I feel sure if they had any feeling of trouble they would not have done that... I even took a photo of the horse parade at the end of the game not during it!! The only photos included in the report were where the excited fans ran on the pitch, the idiots that were removed and the horse parade at the end of the game but taken out of context! I have been a loyal fan for many years and I have seen lots of trouble but I don't think Millwall need or deserve to be tarnished like this any longer! I am avid fan of football in general and I'm disappointed that my local side have had to yet again prove that they are a long way from yesteryear and are on the way forward!! Please feel free to question many supporters through membership as I feel sure they will all say the same that we were not in anyway as bad as the reports have stated. There were no signs of trouble and I had a very enjoyable day!!
By Michelle Gosaage. Posted May 10 2009 at 3:54 PM.
"Mounted police were needed to keep control as dozens of Lions fans invaded the pitch after Neil Harris' winner in yesterday's League One play-off semi-final first leg at the New Den."
i think you will find the horses came on AFTER the game NOT after the goal as your report implies.
By lionsroar. Posted May 10 2009 at 10:09 AM.
i think leeds can overturn this on thursday. we will have the loudest support ever and no london softies can match that.
By david. Posted May 10 2009 at 10:08 AM.
I was at the game yesterday. Yes it was loud, yes the Leeds players got a bit of stick. Yes a few "supporters invaded" the pitch when Neil Harris scored (about 20) BUT it was nothing like your report implies. The atmosphere was great, there was no hint of trouble and to be fair, I think most supporters were more nervous than looking for trouble. And, as Millwall were the better team & outplayed Leeds, their supporters obviously celebrated in style. I'm sure if the similar events happen at Elland Road on Thursday, Leeds fans invade the pitch and David Forde get "abused" by a Leeds fan, that will be Millwalls fault too. No-one likes us and we don't care, but I like them and I do care.
By mum on call. Posted May 10 2009 at 9:07 AM.