CHICAGO (Ticker) -- Things could not be going much better for the Kansas City Royals . For the Chicago White Sox , things could not get much uglier.

Kansas City remained the hottest team in the American League by rallying for four runs in the ninth inning, but Chicago's latest loss, an 8-5 defeat, will be remembered for another disturbing fan incident.

Tuesday's game momentarily was halted after the eighth inning when a fan ran onto the field and attacked first base umpire Laz Diaz. Royals right fielder Brandon Berger , who recorded the final out of the inning with a catch in foul territory, immediately ran to Diaz's aid.

By the time Berger arrived, Diaz had the assailant subdued. Teammates and Diaz's fellow umpires quickly arrived and held the fan until security arrived. The incident was eerily similar to a game between the teams on September 19, when a father and son attacked and injured then-Royals first base coach Tom Gamboa.

"It's a very sad situation," White Sox manager Jerry Manuel said. "It's a bad reflection on Chicago, at least on our side of town. Something has to be done about it. Hopefully in the future, this will not happen again."

"I was just making the catch and I looked up, and I saw the umpire getting tackled," Berger said. "My first instinct was, `Oh no, not again.' When I got there, I got him off of Laz, but Laz turned to me and said, 'That's all right, I think I have things pretty well in hand myself.'"

Coincidentally, Gamboa was in the ballpark as the Royals bullpen coach.

"What can I say? It shouldn't be happening," Royals manager Tony Pena said. "This shouldn't be happening to us every time we come to Chicago. You see fans coming out on the field everywhere, but it seems only in Chicago people are getting attacked. To be honest with you, after that incident, we got our momentum back."

" Chicago White Sox fans are going to have to look themselves in the face at some point and decide if they want to see a baseball game or just have fights all night," Royals first baseman Mike Sweeney said. "It's sick that it's happened to us two times in a row. Luckily, Berger saved the day from anyone else getting hurt."

Following the brief interruption, the Royals erased a 5-4 deficit against Chicago closer Billy Koch (1-1), who surrendered a two-run homer to Sweeney and a two-run single to Berger.

"It seems to be someone different every night," Sweeney said. "It doesn't matter whether we're trailing or not. We feel somebody's going to do something to turn the game around. I guess tonight it was my turn."

The win was the 11th in 12 games for Kansas City.

Koch started the ninth and retired Michael Tucker to open the inning. Joe Randa singled and Sweeney hit a 1-1 pitch over the wall in left-center field for a 6-5 lead.

Koch continued to struggle, walking Raul Ibanez and surrendering a double to pinch hitter Desi Relaford . Berger made it 8-5 with a two-run base hit to left.

Mike MacDougal started the bottom of the ninth for Kansas City and promptly walked Armando Rios and Joe Crede . But MacDougal rebounded to strike out pinch hitter Brian Daubach and D'Angelo Jimenez. Rios then tried to take third on a ball in the dirt and was thrown out to end the game.

Randa got the Royals off to a quick start with a first-inning homer off White Sox starter Mark Buehrle . But Chicago scored three times off Miguel Asencio in the bottom of the frame.

Carlos Lee drew a bases-loaded walk and Rios made it 3-1 with a double to right.

Another RBI double by Rios in the third pushed the lead to 4-1.

Kansas City scored twice in the fifth against Buehrle. A throwing error by shortstop Jose Valentin allowed the first run to score and Sweeney delivered a two-out double that plated Tucker.

After Kelly Wunsch escaped a bases-loaded jam in the seventh, Kansas City tied it at 4-4 in the eighth on an error by first baseman Paul Konerko .

Frank Thomas ' second homer of the season, a blast to left field off Albie Lopez leading off the bottom of the eighth, put the White Sox back on top, 5-4.