In a "very tense and very risky" operation, police still believed a man had a bomb when they burst in to an office in Parramatta, Sydney, where he had barricaded himself and his 12-year-old daughter for 11 hours.



Parts of Parramatta were brought to a standstill yesterday after the man holed himself up in a barrister's chambers with the girl, claiming to have a bomb in his backpack and making demands to police.



After police negotiations with the man broke down, heavily armed officers burst into the building about 8pm, escorting the girl away and arresting her 52-year-old father.



The man's daughter, who was with him throughout the siege, reportedly shouted ''don't hurt my dad!'', after the tactical operations unit entered a barrister's chambers.



Assistant Commissioner Denis Clifford said it was a "very tense and very risky" situation as police were only able to confirm the man did not have a bomb after the siege was over.



"It was certainly a big risk and again I praise the courage of the officers who broke into that confined space, that barricaded space, believing that that person had a bomb," he said at a press conference this morning.



"It's not a decision I made lightly.



"But I made that decision based on a lot of advice from experts in those areas, from the negotiators, from the tactical police, from the bomb squad ... with the safety of the 12-year-old being paramount, but also with the safety of our officers."



The girl, 12, was not physically harmed but was highly distressed and treated by paramedics.



The man's family had complained the siege would have been resolved much earlier if they had been allowed to talk to him.



''If they'd let the family speak to him at two o'clock this would have been all finished by three o'clock,'' the man's brother said.



Mr Clifford said he could understand their frustrations, but it was less risky for trained negotiators to talk to the man.



"What I would say to the family is the man who was barricaded in that situation yesterday is probably not the man that they would be able to sit down across the kitchen table and have a conversation with," he said.



"It was a very stressful, emotional situation that he was in and ... the question is asked whether family, friends, legal representatives should be allowed to talk to somebody.



"It's a big call because we just don't know what the reaction might be from that person."



Mr Clifford said he would not go into detail about yesterday's police operation, or about the demands the man was making.



The man was seen at several points during the siege standing at a window, sometimes shirtless and once wearing a barrister's wig which he spat on.



He was also broke a window with a bottle, threw a phone out the hole and gestured with a bleeding hand.



A Greens MP, Jeremy Buckingham, said he had a short meeting with the man on Monday.



''This man and a girl came to my office at about 2.30pm … and he spoke to me for about five minutes about a legal issue,'' he told Parliament.



''He said he had information he wanted to show the Attorney-General. He did not clearly articulate his issues and I told him I could not help him.''



The man, from Orange, will face Parramatta Local Court today charged with seven offences, including take/detain person with intent to obtain advantage.

The man said to be at the centre of the siege in Parramatta, in Sydney's west.