Foreign minister Murray McCully says it is "heartening" that the Tongan Prime Minister has made assurances the courts would not be subjected to political interference when considering the extradition of a former Fijian Army commander now in Tonga.

Fiji today started the legal process to extradite ex-Fiji Royal Military Force chief of staff Lieutenant Colonel Ratu Tevita Uluilakeba Mara, who was taken to Tonga by its Navy after being charged with sedition.

Mr McCully said New Zealand was watching the issue closely, but would not intervene at this point because it was an issue between Fiji and Tonga.

In a statement today, Tongan prime minister Lord Tu'ivakano said Fiji was free to apply for his extradition and Tongan judges were not subject to influence from either the King or his ministers nor were they encouraged to pass judgments according to their political beliefs.

Mr McCully said it was "a heartening approach in the circumstances."

He said New Zealand would leave it for Fiji and Tonga to resolve between themselves, although he was keeping a close eye on the matter.

He had not spoken to Tonga's Prime Minister and said he had not sought any information on how Lt Col Mara had come to be picked by Tonga's Navy.

Fiji prime minister Commodore Frank Bainimarama has declared ex-Fiji Royal Military Force chief of staff Lieutenant Colonel Ratu Tevita Uluilakeba Mara a fugitive and accused the Royal Tongan Navy of illegally picking up Lt Col Mara in a patrol boat in Fijian waters last week.

Suva Magistrates Court this morning issued a bench warrant for Lt Col Mara, who breached his bail conditions after being charged with one count of uttering seditious comments, Radio Fiji reported.

The bench warrant means Fiji can proceed with an extradition application under the Extradition Act.

Lt Col Mara, who has strong Tongan connections, was now reported to be under Tonga's protection.

"When I was rescued by the Tongan navy, I asked to be brought to Nuku'alofa, where with the sure protection of King George's government I shall be able to tell the truth without fear of retribution about the tragic oppression that stifles my beloved land," Lt Col Mara said.

He is a son of late Fiji president Ratu Sir Kamisese Mara. Along with Brigadier General Pita Driti, a high ranking commander, Lt Col Mara was charged a week ago with mutiny and accused of trying to overthrow the Bainimarama regime.

Lt Col Mara has since released a You Tube video strongly critical of Fiji's attorney-general Aiyaz Khayum, and said Cdre Bainimarama "is no more than Aiyaz Khayum's hand-puppet".

Cdre Bainimarama told FijiLive said the extraction was illegal and he would talk to the Tongan King.

Police had started investigating how Lt Col Mara escaped Fiji.

"This is unfortunate and shows a fundamental disloyalty to Fiji, Fijian laws and the Fijian people," Cdre Bainimarama said.

The diplomatic situation between Tonga and Fiji has recently been tense, with both laying claim to the Minerva Reef which lies between the two countries.

In a You Tube video dated May 14 entitled "regime change should happen in Fiji soon", Lt Col Mara said the plan to arrest him and Brig Gen Driti on what he said were "trumped-up" charges had been laid by Mr Khayum.

"For inexplicable reasons, Commodore Bainimarama, weakened by ill health, morally and intellectually bankrupt, is no more than Aiyaz Khayum's hand-puppet," Colonel Mara said.

"His (Khayum's) megalomania is inspired entirely by the self-importance of a lonely and inadequate man, endowed with no leadership qualities and incapable of understanding the simplest principles of decency and respect."

Lt Col Mara said that when Fiji's dictatorship had ended, "all of us who once served it shall answer to the Fijian people for the part we played, and I shall gladly submit to their verdict".

- NZ Herald, NZPA