Riots broke out at Beirut's race track when four horses favored by bettors tripped and fell at the start of a race Tuesday. Hundreds of losing bettors angrily pushed through fences and police cordons to block the track after the spills allowed Commodore, a 91-1 long shot, to win the day's third race.

The protesters formed a shoulder-to-shoulder wall across the field while others tore down brass posters carrying the results and the names of the riders in the next race.

After a 15-minute standoff, it was announced that the third-race result was canceled and all bets would be refunded. But just as the horses came out for the fourth race, a man jumped from the stands, waving a $12 win ticket on Commodore and threatening to blow up the track unless he was paid.

Police escorted him from the track, located on the Green Line that divides Beirut into Moslem and Christian sectors. A few minutes later, a rocket-propelled grenade blasted through the track wall, causing panic in the crowded stands but no casualties.

The three remaining races on the program were canceled.

The name of the track: the "Palace of Peace."