Nauru's parliament has re-elected its president David Adeang unopposed after the Micronesian nation's recent election.

But it was the controversial decision by 18 other members inside its 25th parliament on Tuesday that could have deep ramifications for transparency in Nauru's fragile democracy.

Nearly 8,400 voters from about 12,000 residents cast their votes in Saturday's poll.

Mr Adeang was re-elected to parliament with 837 votes in the Ubenide constituency - one of eight electoral areas across the tiny 21 km2 island - in which he faced 11 opponents.

Marcus Stephen, a former Commonwealth Games seven-time weightlifting gold medallist, was re-elected by MPs as the speaker of the parliament before calling for nominations for president.

Mr Adeang's last presidential term featured autocratic traits which shocked some of Nauru's Pacific neighbours.

Nauru, which received up to $46 million from Australia last financial year, according to the Department of Foreign Affairs and Trade's development assistance budget estimates, left its donor in the dark just two months ago when it signed a contract with a Chinese government company.

The decision, a month before its parliament had been dissolved ahead of the election held every three years, was not flagged with his Nauruan government or its cabinet of eight ministers.

The two countries hold a treaty pact that demands the Australian government are handed notice of prospective security and critical infrastructure deals.

The funding is also in exchange for an effective veto of other agreements with foreign third-party powers, especially China, which is exercising their influence in the Pacific in recent years.

Foreign Affairs department officials only found out about the $1 billion infrastructure investment proposal signed between Nauru and a China Rural Revitalisation and Development Corporation from a media release.

The Republic once had a thriving phosphate industry until more than 80 per cent of the island was strip-mined bare in 2000 and has remained environmentally damaged in the ensuing years.

Past Nauruan governments were able to pay its citizens wealthy proceeds of phosphate deposits throughout the 1970s and 1980s.

To reinvigorate the economy, Nauru has sold its first golden passports this year for $160,000 each to foreigners after Mr Adeang said the raising of funds would relocate residents to higher ground in the face of rising sea levels.

It launched the scheme in February to offer citizenship by investment, claiming passports will enable recipients visa-free entry into 89 countries.

But Mr Adeang had also orchestrated a plan for Nauru to open its waters to deep sea mining back in 2021.

The 55-year-old president appealed to the International Seabed Authority to quickly draft rules that would allow Nauru to gain global approval to let companies explore and mine the island's ocean floor.

"As both a small-island developing state and also a sponsoring state for deep seabed mineral exploration, Nauru has invested significantly through our sponsored entity to access minerals essential to powering the world's transition away from fossil fuels and advancing the common heritage of humankind," Mr Adeang told the recent United Nations General Assembly.

"We've consistently advocated for robust regulations that balance responsible mineral recovery with effective environmental protection."

A veteran Pacific correspondent that had spent years visiting Nauru sent out a warning, telling a Radio New Zealand podcast that Mr Adeang had proven to be contemptuous of scrutiny.

Journalist Barbara Dreaver was once detained for interviewing a refugee at an Australian detention camp in Nauru while attending its Pacific Islands Forum leaders' summit.

She first pointed out that Mr Adeang's close relationship with Baron Waqa, who was president of Nauru from 2013 to 2019, was alarming.

"Both (Mr Adeang) and Baron Waqa were accused of taking kickbacks from a phosphate company, and that's been investigated by the Australian police," she said in the podcast.

Both men have denied the allegations, but Waqa, the current Pacific Islands Forum's Secretary-General, overlooked this year's Nauruan elections, praising the country's "dedication to electoral transparency and credibility".

Ms Dreaver said ongoing circumstances made it difficult to scrutinise the Nauruan government.

"He sacked a whole lot of judges," she said.

"He changed the judicial system while he was justice minister and he was also a part of this government that has really cracked down on media."

An independent Australian research report into the state of the media found it was run by the state-owned media platforms run of the Nauru Media Bureau.

All journalists in Nauru are classified as public servants and are forced to take an oath of allegiance to the government.

Foreign journalists, who wanted to report in Nauru, have to obtain a visa at a cost of an $8000 application fee.

"It's a great way of controlling the media without saying we're controlling the media," Ms Dreaver said.