A copy of the deal -- signed during a state visit to China that has been criticised by former colonial ruler New Zealand -- showed it covers working together in the "exploration and research of seabed mineral resources".

A joint committee would oversee the partnership, which also includes seabed minerals-related training and technology transfer, logistics support, and deep-sea ecosystems research.

The Cook Islands government said the memorandum of understanding, signed with China on February 14, did not involve any agreement to give an exploration or mining licence.

Cook Islands Prime Minister Mark Brown had already released details of a broader partnership agreement signed during his state visit to China this month.

On Saturday, his office also published three others: the seabed minerals deal; a maritime industries agreement; and a Chinese development aid grant of 20 million yuan (US$2.7 million).

The self-governing Cook Islands, a country of 17,000 people, has a "free association" relationship with New Zealand, which provides budgetary assistance as well as helping on foreign affairs and defence.

Cook Islanders hold New Zealand citizenship.

Brown said the seabed minerals deal supported the partnership pact he signed in China for the two countries to cooperate in trade, investment and the seabed minerals sector.

"Our seabed minerals section remains under strict regulatory oversight, ensuring that all decisions are made transparently and in the best interest of the Cook Islands and its people," he said in a statement.

- New Zealand unnerved -

New Zealand has already accused the Cook Islands government of a lack of consultation and transparency over the wider partnership agreement with China.

It has demanded to see all the agreements signed during Brown's China trip.

"We note the release today of further agreements signed by the Governments of the Cook Islands and China," said a spokesperson for New Zealand Foreign Minister Winston Peters.

"We will now analyse the contents of these agreements -- focusing on the implications they have for New Zealand, the Cook Islands people and the Realm of New Zealand."

New Zealand and its allies including Australia and the United States have been unnerved by China's growing diplomatic, economic and military influence in the strategically important Pacific.

But Brown has insisted his country's relations with New Zealand and other partners are not affected by the partnership accord he signed with China.

The Cook Islands has licensed three companies to explore the seabed for nodules rich in metals such as nickel and cobalt, which are used in electric car batteries.

Despite issuing the five-year exploration licences in 2022, the Cook Islands government says it will not decide whether to harvest the potato-sized nodules until it has assessed environmental and other impacts.

The Pacific country's prime minister has nevertheless touted the benefits of the potentially multi-billion-dollar industry, saying previously that the Cook Islands needs to protect itself against climate change "through whatever revenues that we can get".