A man who set himself on fire outside the Sydney office of the Department of Immigration and Border Protection forced the evacuation of about 50 people seeking passports and left bystanders with nightmare memories.

A witness, who asked not to be identified, said she remains haunted by the sound of his agony as the flames took hold.

“He was screaming in pain – wailing, agony, uncontrolled screaming,” she told AAP.

The man, believed to be in his 30s and described by witnesses as being of Middle Eastern appearance, doused himself in petrol on Lee Street near Central Station about 1.30pm on Friday.

Police negotiated with him for up to 10 minutes before he ignored their pleas and ignited his fuel-soaked clothes.

A police officer who had armed himself with a fire extinguisher during the tense standoff ran to his side and doused the flames engulfing the man’s lower body.

“He was yelling and was completely crazy,” bystander Claude Evans told The Daily Telegraph. “Police did everything they could.”

Another witness told the Nine Network he was screaming, “I want to stay!”

A series of CCTV images shows the man at first sitting with his back against a ramp leading to the office building’s entrance while police stand warily to one side.

A second image, captured seconds later, records an orange  glow around his thighs as the flames erupt.

The NSW Fire and Rescue hosed the man down to dilute the petrol after police doused the fire. The man suffered superficial burns to his thighs and is being treated in hospital.

Detective Superintendent David Donohue declined to detail the man’s background or grievance, apart from describing him as “a deeply disturbed and upset individual” and saying “he was known to police.”

“I’m not at liberty to discuss what his issues were, but he was protesting at the Immigration Department this afternoon, and he’s a person who suffers mental illness,” the detective told reporters in Sydney.

“As you’d appreciate, this could have been a lot worse had police not acted so quickly and put him out,” he said.

“At its highest, he would have killed himself.”

Det Supt Donohue said the man was unlikely to face charges.

“We’re more concerned about his mental health status and we’ll be treating it as such,” he said.

-with AAP

• Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14 or Suicide Call Back Service 1300 659 467.