Mike Tyson is back, a little rusty, a little chastened but very much in control.

"How dare they challenge me with their primitive skills," Tyson said after stopping Frank Bruno in the fifth round Saturday night and keeping Bruno from becoming the first British fighter to win the heavyweight championship in this century.Tyson looked a bit primitive himself as he engaged in a mauling match with Bruno, a match that almost ended as soon as it began when Tyson knocked Bruno down with two right hands 14 seconds into the fight.

"I knew he wasn't hurt as badly as everybody thought," Tyson said. "I didn't hit him with a solid shot."

The champion also admitted that the thought crossed his mind that "it looks like it could be a long fight."

Bruno got up immediately and, as a crowd of more than 9,800 at the Las Vegas Hilton roared, took a mandatory eight-count from referee Richard Steele.

Bruno then fought well and just as dirty as Tyson until the end came with five seconds left in the fifth round.

"When fighters come to fight the heavyweight champion they automatically become a better fighter," Tyson said.

Bruno, however, lacked the arsenal to stay with one of the most menacing fighters in recent years.

In the fifth round, Tyson hurt Bruno badly with a right to the head, then had him reeling with a barrage of punches. Many missed, but many found their mark and it was obvious that Bruno's challenge was nearly at the end.

As the red lights on the corners blinked to signal there were 10 seconds left in the round, Bruno went to the ropes where Tyson unleashed a flurry of punches that included a crashing right uppercut and a left to the head. Bruno's manager leaped onto the apron to stop the fight. Steele beat him to it.

"It's great to be back and hear the crowd," Tyson said after returning to action for the first time since knocking out Michael Spinks in 91 seconds in June. This time he fought without a wife and without his longtime trainer Kevin Rooney.

Tyson divorced actress Robin Givens on Valentine's Day and split with Rooney because of the trainer's public comments about his marraige.

Jay Bright, a longtime Tyson friend, and Alan Snowell trained Tyson for this bout.

"Maybe if Kevin Rooney is there, it doesn't go five," said Rooney, contacted in Schenectady, N.Y., where he was handling some amateur fighters. He did not see Tyson's victory. "When Kevin Rooney was in the corner, Michael Spinks was gone in 91 seconds."

However, the fact that the performance by Tyson, a 10-1 favorite, was not as devastating as his previous victory could be laid to ring rust.

Tyson also said, "I was a little anxious. I wanted to take him out. I was in good shape, but I could have used more time in training. That's not an excuse."

After Bruno bounced up in the first round, he landed a hard left hook that appeared to wobble Tyson.

"He threw a great deal of hard punches, but I refused to go down," Tyson said. "They didn't faze me. He didn't hurt me because I refused to be hurt. The punches were very solid. I felt them. They made my legs twitch."

The 27-year-old challenger, who outweighed Tyson 228 to 218, said, "I felt him crumble a little" from the hook in the first round.

Bruno was warned several times for holding with his left hand behind Tyson's neck while hitting the champion with his right. And when he spun Tyson and hit him on the back of the head, Steele deducted a point in the first round.

About the blow to the back of the head, Tyson said, "It felt like my head was coming off."

Tyson, on the other hand, landed some elbows and forearms. And after the bell sounded ending the third round, he nailed Bruno with a left hook.

"What about a point for that" a Bruno cornerman shouted at Steele.

Before the fight, Tyson promised to avoid long layoffs, although continuing litigation with manager Bill Cayton could tie the fighter up. Tyson has sued Cayton in an effort to break his managerial contract and has joined forces with promoter Don King.

King has said that Tyson's next opponent could be Joe Ribalta, a Cuban living in Miami whom Tyson knocked out in the 10th round back in 1986, two fights before he won the World Boxing Council share of the title with a second-round knockout of Trevor Berbick.

Tyson earned about $8 million for his sixth defense of the undisputed title and his 10th championship appearance. His record now is 36-0 with 32 knockouts.

Bruno got $3.8 million from his second shot at becoming heavyweight champion. He was stopped in the 11th round by Tim Witherspoon in a bid for the World Boxing Association title in 1986 in London. The 27-year-old challenger's record now is 32-3 with 31 knockouts.

Bruno's challenge was the 13th by 11 British hjeavyweights. The last British fighter to win the world title was Bob Fitzsimmons, who beat James J. Corbett in 1897 and lost to James J. Jeffries in 1899.

While Bruno did not win a round on the Associated Press card, he did keep Tyson from becoming the third heavyweight champion to score consecutive first-round knockouts.