Copenhagen, Denmark (AP) - Six rounds not only gave Mike Tyson some much needed work, it may also have gotten him another shot at the heavyweight title.

In his longest fight since losing his title to Evander Holyfield five years ago, Tyson bloodied Brian Nielsen and knocked him down Saturday before the bout was stopped with the half-blinded Dane still on his stool after the sixth round.

Though stopped between rounds, the fight was declared a technical knockout one second into the seventh.

"I'm back," Tyson said, after ridding himself of some ring rust in his first fight in nearly a year.

He kept his spot as the mandatory No. 1 challenger for the winner of the Nov. 17 fight between Hasim Rahman and Lennox Lewis. And he did it at the heaviest weight of his career, showing the boxing world a new, bulked up Tyson as he chases the heavyweight title for a third time.

He indicated, however, he may need a few more rounds first.

"I felt pretty good, but I felt rusty and little unsure," the 35-year-old Tyson said. "... I'll fight anyone, but I need two more fights for a title fight. Two more and I'll be ready."

Six rounds are the most for Tyson since Holyfield stopped him in the 11th round on Nov. 9, 1996, for the World Boxing Association title.

Fighting at 239 pounds -- nearly 20 pounds heavier than his normal fighting weight -- Tyson seemed happy to get something of a workout. After all, he had gone less than five full rounds in his four previous bouts combined.

His last fight was against Andrew Golota, who quit in the second round last October.

Tyson improved to 49-3 with two no-decisions and 43 KOs. Nielsen dropped to 62-2 with 43 KOs.

Tyson cut the Dane over his left eye in the second round and flattened him in the third. The referee finally ended the scheduled 10-rounder with Nielsen still in his corner, his eye swollen shut.

Tyson won every round and rocked Nielsen consistently. It was only the second time the Dane has been knocked down as a pro or amateur. He has never been knocked out.

"I felt like I was hurting him with a few of my punches," Nielsen said. "The referee stopped it, but my corner asked that he stop it."

Referee Steve Smoger asked Mike Hall, Nielsen's American trainer, to confirm the boxer wanted to stop.

"I want to hear it from his mouth. You understand you lose," Smoger said. Nielsen said, "Yes."

"The last few punches I couldn't see. I did the best I could. I'm very disappointed. I hope that now people will give me some respect. I am a fighter," he said.

Nielsen had vowed to beat Tyson black and blue, but Nielsen was the only one absorbing the heavy punches in this fight.

Tyson entered the ring wearing a baby blue hooded sweatshirt with "NEW YORK" embossed on the front and a knit cap with "PUNISHMENT" across the front. Some fans tossed plastic ears onto the canvas -- a reminder of Tyson's famous "bite fight" with Holyfield.

Nielsen's theme song was "Always Look On The Bright Side Of Life," from the Monty Python movie "Life of Brian." Singing along was a heavily partisan crowd of 25,000 in Parken Stadium.

Tyson quickly pinned Nielsen on the ropes with a series of punches and connected with one big left uppercut. The Dane was able to cover up and hang on with Tyson seeming to tire late in the round.

In the second, Tyson landed a good uppercut, and Nielsen covered up on the ropes. Tyson bloodied Nielsen above the left eye with a right hook just before the bell.

Nielsen's eye began to swell in the third round, with Tyson rocking the Dane a few times and complaining that his opponent was grabbing and holding. Late in the round, Tyson knocked Nielsen down with a left-right combination. As the bell rang, Tyson hit Nielsen with a low right hand, sending him staggering into the ropes.

Nielsen, 259 pounds, tried to slow the fight in the fourth by hanging onto Tyson, who rocked him with a left jab.

The fifth was more of the same with Nielsen's left eye swelling shut. But the pace slowed, and Nielsen landed one of his best shots of the bout with a right hand. Seconds later, Tyson hit him with a right-left that again had the Dane staggering.

Tyson opened the sixth with a big jab but seemed less willing to attack. He also jarred Nielsen with a left uppercut and a right hand before the bell.

"He took some real shots," Tyson said. "He put on a heck of a fight. I had no idea he was that tough as a fighter. I didn't have an easy night, I was trying to hit him anywhere.

"Around the fifth round I said, `This guy came to fight.' " He was trying to push me as much as possible and I tried to hit him as hard as I could," Tyson said.

This fight was the third of Tyson's last four to be held outside the United States. The others were a second-round win over Julius Francis on Jan. 29, 2000, in Manchester, England, and a 38-second win over Louis Savarese on June 24, 2000, in Glasgow, Scotland.

Since being released after serving three years on a rape conviction, Tyson has now fought 12 times.

Tyson, who said he plans to stay in Europe after the fight, is reportedly heading for France.

Nielsen brought an impressive record and a lot of confidence into the fight, but it was a record built on no-name and over-the-hill fighters. His best-known opponents were former champions Larry Holmes and Tim Witherspoon, who were both in their 40s when Nielsen beat them.

While Tyson's second fight with Holyfield was the richest ever and did lucrative pay-per-view business, Saturday's bout was taped for a delayed showing on the Showtime network.