RIVERSIDE (California) - A SERIAL arsonist started a California forest fire that left five firefighters dead as part of a plot to stop his pit bull terrier from being euthanised, a court heard on Thursday.

Prosecutors in Riverside, 90km east of Los Angeles, said Raymond Lee Oyler was a man 'bent on destruction' who had started the October 2006 fire out of anger that his dog had been impounded.

Oyler, 38, faces five counts of murder and 40 arson-related counts and faces the death penalty if convicted.

'The Esperanza Fire burned over 43,000 acres and took the lives of these five brave men,' Mr Hestrin told jurors. More than 50 houses and buildings were destroyed in the fire.

Oyler was a 'a man bent on destruction, a man with the desire to be important and so great (that he would) unleash a disaster of his own making,' Mr Hestrin added.

The US Forest Service firefighters killed in the fire were attempting to save people who had not been evacuated when their truck was overrun by flames.

Mr Hestrin said prosecutors would use statements from Oyler's girlfriend that he confessed to setting fires and wanted to set a hill ablaze as a distraction so he could rescue his quarantined pit bull terrier that was to be euthanised.

Authorities traced the fire back to Oyler when they caught his car on a surveillance camera several times and retrieved matches from the crime scenes that were identical to those found at his girlfriend's home.

In addition, a witness at a gas station near the Esperanza fire identified Oyler as standing in the parking lot admiring the blaze, saying it was 'acting exactly as I thought it would,' Mr Hestrin said.

Defence lawyer Mark McDonald said Oyler had not started the Esperenza fire and discounted the prosecution's suggested motivation, saying the defendant's dog had already been released by the time of the fire.

The trial is expected to take a month. Oyler remains jailed without bail.