Police regret violent fugitive's siege death

South Australian police pleaded with violent fugitive Rodney Clavell to give himself up peacefully before he was found dead at the end of a 12-hour police siege in Adelaide, South Australian Assistant Police Commissioner Paul Dickson said.

Mr Dickson said it was still not clear whether four women who had been with Clavell in a massage parlour in Adelaide's CBD during the siege were hostages or if they knew the 46-year-old.

He said a police robot entered the first floor of the building, where Clavell had been holed up, just before 1pm. The robot located Clavell's body about 1.40pm.

"Unfortunately today's planned activities by the police didn't work out as we had hoped," Mr Dickson said.

Four women had been released about 11.30am after hours of negotiations with Clavell by police through the women. Police tried for hours to end the siege peacefully, Mr Dickson said.

One of the women collapsed to the ground after walking from the building with her hands kept high above her head and became emotionally distressed.

Mr Dickson said police attempted to contact Clavell once the women walked from the building but he did not respond so a police robot was sent in. Police officers then entered the building.

Because of the circumstances his death will be investigated as a death in custody, Mr Dickson said.

He said police had not been able to speak with Clavell directly throughout the siege that began in Marilyn's Studio, which provides adult services, in King William Street from 1am on Thursday.

Parts of Adelaide's city centre had been in lock down. SMH/AAP