A MAN who barricaded himself and a girl inside a law office - claiming to have a bomb - was taken into custody last night following an 11-hour siege in Sydney's second-biggest CBD.

Police armed with a battering ram, chainsaw, axe, crowbar and gas cylinders stormed into the building on George St, Parramatta, shortly before 8pm.

By 8.10pm a 12-year-old girl was led screaming from the building by police before being placed in an ambulance.

Shortly after, the 52-year-old man was taken into custody, ending a siege that began when he stormed into legal chambers in Parramatta about 9am, saying there was a bomb in his backpack.

Relatives of the man last night lashed out at the police response, saying the siege could have been ended hours earlier if they were given the chance to talk to him but their requests were denied.

"I believe if they would have let the family speak to him at 2pm this would have been finished by 3pm," the man's brother said.

Assistant Commissioner Dennis Clifford said negotiations broke down last night and police were forced to storm the premises. He said the girl was very distressed but not hurt.

Bomb technicians last night were carefully examining the backpack.

It is alleged the man had visited NSW Parliament House in Macquarie St the day before to complain about the legal system.

He had tried to force his way into the office of NSW Attorney-General Greg Smith before security guards were called and he was escorted out of the building.

The Herald Sun can reveal the man was a prominent Aboriginal activist in the 1980s and '90s who played a major role in a NSW race riot in 1987.

He badly cut himself after smashing a hole in a window with a glass bottle during the siege. Just before 6pm he threw a note out the window.

He is expected to be charged and appear in court this morning.

- with Mark Morri

Originally published as Safe end to Sydney siege