Terry Mills has arrived back in Australia after being ousted as Northern Territory chief minister in a leadership coup.

Mr Mills was in Yokohama on a trade mission when he was told by phone yesterday that he had been dumped in favour of Country Liberals colleague Adam Giles.

Mr Giles becomes the first Indigenous head of government in Australian history, while Dave Tollner will be the new Deputy Chief Minister.

Mr Mills arrived in Sydney on a Qantas flight this morning and is now expected to head to Darwin.

Who is Adam Giles? NT Chief Minister and Australia's first Indigenous head of government. The 40-year-old father of one is the Member for Braitling. He was born in the Blue Mountains region of NSW and studied accounting and real estate. Worked in public housing management for the ATSIC. Then moved to Canberra and worked for the Department of the PM. In 2004 he stood as the Liberal candidate for the ACT electorate for Fraser. He later settled in Alice Springs, and stood as a CLP candidate for Lingiari in 2007 He lost, but was elected to the seat of Braitling in 2008 Territory election. He became Transport Minister after last year's election.

Speaking to ABC Local Radio Darwin yesterday, he said he would "do the honourable thing in support of the Territory" and step aside.

He said Mr Giles "probably" had the experience and leadership skills to be Chief Minister.

"He will have my support because I am here to serve the best interests of the Territory," Mr Mills said.

"It's easy to pass judgment on how a Chief Minister should operate.

"Whether he has that mantle ... I'll be there to support if he requires it because it is a very challenging role.

"It's been an honour for me to have carried that responsibility for some time."

Mr Mills said he would decide his next move after speaking to his wife, and added that yesterday's events had thrown up some "deep questions" about his future as a politician.

But he said it was "not my style" to leave the CLP.

"I step aside (as chief minister)... what I do after that decision is something I will think about.

"I'll go back and talk to people and my main business is to make sure we get on with the job of serving the Territory well."

'Truly humbled'

Sorry, this video has expired Giles 'truly humbled' to be new NT leader

Mr Giles, who had a bid for the top job stifled by colleagues last week, fronted the media late yesterday afternoon and said he anticipated the swearing-in ceremony take place today.

He did not take questions.

"Can I say I am truly humbled to be asked by my colleagues to take on this role," he said.

"It is a significant challenge to take the leadership of the Northern Territory and the times we're in at the moment and I look forward to that role.

"I think there is a great message to sell by the Country Liberal Party and I look forward to taking us into the future, not only with my deputy leader elect Dave Tollner but all my colleagues and Cabinet."

He also thanked Mr Mills for his service to the party and the Territory.

"I do count him as a friend and I wish him all the best and look forward to him continuing his role in Parliament," Mr Giles said.

Opposition education spokesman Michael Gunner says the move is gutless.

"This confirms that the CLP is divided, every leadership challenge confirms division," he said.

But Country Liberals president Ross Connolly says he hopes the change at the top helps resolve tensions within the party.

He says the change has meant a "substantial" shift of interests within the parliamentary wing of the party.

Mr Mills's dumping is the second such development in a week, coming after Ted Baillieu's replacement as Victorian Premier last Wednesday.