A stricken container ship wedged on a reef off a popular New Zealand holiday spot has broken up but is still on the reef after running aground three months ago, maritime authorities said on Sunday.

The 47,230-tonne Liberian-flagged Rena has been stranded on a reef 22 km miles off Tauranga on the east coast of New Zealand's North Island since running aground on October 5.

There has been a significant change in the status of the Rena overnight, with the ship separated into two pieces that are now 20-30 metres apart, Maritime New Zealand spokesman Ross Henderson said in a statement.

The forward section of the ship is in its original position on the reef, with the stern section broken away and moving significantly, but still on the reef.

Henderson said the 236-metre ship was pounded by wild weather overnight, with weather conditions expected to remain poor for the next three to four days.

The maritime authorities said there has been a significant discharge of containers and container debris from the ship, which may lead to an extension of the current exclusion zone.

On Friday, the authorities said 881 containers were still on board, having removed 389 from the cargo ship while around 98 containers were believed to have been lost overboard.

Salvage teams have pumped more than 1,000 tonnes out of the ship while some have remained onboard.

The National Response Team has been activated to respond to the potential release of fuel from the ship and to treat any affected wildlife.

Rena's captain and navigation officer, both Philippine nationals, have been charged with operating a vessel in a dangerous manner, and releasing toxic substances, which carry maximum fines of NZ$300,000 or two years in prison.

They are due to reappear in court next month.

The vessel is owned by Daina Shipping, a unit of Greece's Costamare Inc. and was under charter to Mediterranean Shipping.

(Reporting by Mantik Kusjanto)