Immigration Minister Chris Bowen says the first 19 people sent to Manus consisted of seven families of Sri Lankan and Iranian origin.
They arrived this (Wednesday) morning, accompanied by Australian Federal Police, immigration staff, interpreters, children's services and medical staff.
"The first transfer to Manus Island has now taken place - and will be the first of many - sending the clear message that people arriving by boat risk being sent to a regional processing centre in either Nauru or Papua New Guinea," Mr Bowen said today.
The four children are the first the government has sent offshore since embracing its tough new policies in August.
Operations at the Manus centre will be overseen by both the Australian and PNG governments, with welfare services provided by the Salvation Army, health services by IHMS and operational support services by British security firm G4S.
Local Manus Island residents have also been employed at the processing centre.
Mr Bowen also announced that specialised children's services on Manus Island would be provided by Save the Children, including child protection and education activities.
Mr Bowen also announced the creation of an advisory committee to play an oversight role for the Nauru centre.
It will be chaired by immigration department Deputy secretary Wendy Southern and Nauru MP Mathew Batsiua. It also includes Nauruan Justice Secretary Lisa Lo Piccolo and refugee policy expert Paris Aristotle.
The government has also announced preliminary interviews for the processing of people at the Nauru centre will begin soon.
"It is expected that assessment of claims will fully commence in early 2013," he said.
A contract has been signed with the company Canstruct for work on the permanent facilities at Nauru.
Mr Bowen also revealed another 100 Sri Lankan men have been sent home involuntarily, the ninth such removal this month.
This takes to 426 the number of Sri Lankans forced to return home since August 13.
A total of 525 have now gone back, including 99 who have gone voluntarily.
As well, the government has for the first time forcibly returned an Afghan man found not to be a refugee.
Mr Bowen announced the Pontville Detention Centre in Tasmania will reopen to relieve pressure on the onshore processing network.
Capacity at the Melbourne Immigration Transit Accommodation will also be increased by about 300 places.
Asked how long asylum seekers could wait to be processed at offshore centres, Mr Bowen said, "The five-year figure is an accurate one."
"I've said repeatedly that the no-advantage test will mean that people will wait for a very substantial period," he said.
"Could it be five years? Yes it could."
Mr Bowen also dismissed Amnesty International's comments that Nauru's processing centre was "completely unacceptable".
"Amnesty International opposed the Nauru processing facility before they got there, they oppose it after they leave," he said.
Asked whether Australia's asylum seeker policy might be seen as cruel, Mr Bowen said the government had an "overriding moral and humanitarian obligation" to stop people drowning at sea.
"And yes, that means difficult decisions must be taken," Mr Bowen said.
"There is nothing moral, nothing humanitarian, nothing acceptable about the types of deaths, of drownings, we've seen of people coming to Australia by boat."