Thousands of basketball fans began converging on downtown Los Angeles early Wednesday as the city prepared to salute its NBA Championship-winning Lakers.

Several hundred police officers were out in force for the victory parade, which was to begin at the Lakers' Staples Center at 11:00 am (1800 GMT) before finishing with a rally at the Los Angeles Memorial Coliseum.

Local television reports showed large crowds of fans lining the parade route while seating at the Coliseum, venue for the 1984 Olympic Games, was already beginning to fill out.

The parade comes after the Lakers clinched the NBA finals series on Sunday with a victory over the Orlando Magic in Florida.

The win triggered ugly scenes near the Staples Center on Sunday, with a minority of fans starting fires, smashing cars, looting stores and hurling missiles at police officers, leading to 18 arrests.

Los Angeles Police Department chief William Bratton warned troublemakers at Wednesday's parade would meet with a "zero tolerance" approach.

"Anyone who wants to come in to this event to disrupt it, to celebrate themselves rather than the Lakers, stay home," Bratton said.

"If you come in and you're drinking, you're drunk and you're misbehaving, you're going to be arrested," he said. "Clear and simple. We're going to have a very significant number of officers in that crowd -- plainclothes and uniform. We will have zero tolerance for any type of misbehavior."

Lakers star Derek Fisher also called for fans to celebrate respectfully.

"We don't want to have one person or one small group of people ruin this opportunity for us all to have a great day for the team and organization to be recognized," Fisher said. "Let's keep it safe."

Despite complaints over the 2-million-dollar bill for the parade, the cost to the city had been reduced after donations of around 850,000 dollars by wealthy individuals in Los Angeles, local media reported.

The Lakers and the owners of the Staples Center had contributed another 1 million to the cost.