US police were searching Thursday in and around a California mountain resort for an alleged fugitive cop killer, after his car was found burnt out in nearby woods, officials said.

Schools and ski lifts around the town of Big Bear, about two hours east of Los Angeles, were put on lockdown after reports of the burning vehicle matching the description of that used by Christopher Dorner, 33.

A few hours later, San Bernardino County Sheriff John McMahon confirmed the Nissan pickup truck was indeed that used by Dorner overnight in the LA suburb of Riverside in an ambush on two policeman, one of whom died.

"We'll keep working on it until we're able to either locate the suspect, or determine that he's no longer in the Big Bear Valley," McMahon told reporters, adding that LA Police Department officers were helping in the search.

Police launched a massive manhunt overnight for Dorner, a former policeman suspected of killing three people, including a policeman, and injuring two others after posting a chilling manifesto online.

Dorner, angry at being sacked from the LAPD in 2008, promised to "bring unconventional and asymmetrical warfare to those in LAPD uniform whether on or off duty," unless his name was publicly cleared over his dismissal.

The search has produced several false alarms, including an incident in which police injured two civilians near Los Angeles after mistaking their vehicle for Dorner's, and the lockdown of a naval base near San Diego.

LAPD chief Charlie Beck warned that Dorner was considered "armed and extremely dangerous," adding that the suspect has "multiple weapons at his disposal, including assault rifles."