LOS ANGELES (REUTERS) - A 20-year-old Indiana man who was arrested on his way to a Los Angeles-area gay pride parade after police said they found guns and bomb-making chemicals in his car was charged on Tuesday with unlawful possession of an assault weapon and explosives.

James Wesley Howell was taken into custody early on Sunday morning in the Los Angeles suburb of Santa Monica and police officials say he told arresting officers that he planned to attend the pride event in nearby West Hollywood.

Authorities have since said there was no apparent link to the deadly mass shooting hours earlier at a gay nightclub in Orlando, Florida, where a gunman killed 49 people..

Howell was taken into custody shortly after 5am on Sunday after officers responding to reports of a man knocking on a window found him sitting in his white Acura with three assault rifles and high-capacity magazines, according to the Santa Monica Police Department.

Also found in the car was a 19-litre bucket with chemicals that could be used to make an improvised explosive device.

Santa Monica Police Chief Jacqueline Seabrooks initially said on Twitter that Howell told officers he wanted to "harm" the gay pride festival. But Seabrooks later called that information inaccurate and that Howell had only told officers he planned to attend the event.

"The suspect did make an initial statement to the effect that he was going to go to the pride festival," the department's Lieutenant Saul Rodriguez told reporters on Sunday.

"Beyond that he did not make any additional statement saying that he was going to do anything further than that. We do not have any additional information related to what his intentions were," Rodriguez said.

In charging Howell with the weapons charges, three felonies and one misdemeanor, Los Angeles prosecutors made no comment on what they believed his plans might have been.

He was scheduled for an initial court appearance later on Tuesday and prosecutors said they would ask that he be held on US$2 million (S$2.7 million) bail.

An FBI spokesman said that agents had executed a search warrant at Howell's residence in Clark County, Indiana, on Monday evening as part of a joint investigation with local authorities. The FBI did not say what it found in that search.

The Los Angeles Times has reported that Howell was charged in Indiana in October 2015 with pointing a loaded firearm at an ex-boyfriend and that he had pleaded guilty in April to misdemeanor intimidation.