THOUSANDS of people who posted messages of hate and threats on the internet relating to accused arsonist Brendan Sokaluk in the days after he was charged potentially face serious criminal charges, lawyers and internet regulators warn.

Since Friday, at least five groups on social networking site Facebook had attracted about 3500 people, with most users either threatening or inciting violence towards the accused.

"Burn him like he burned those innocent people … just a lot slower," wrote one man.

Another man, who described himself as a volunteer firefighter, said the accused arsonist "deserves to suffer".