Foreign Affairs Minister Murray McCully is condemning North Korea's launch of a long-range rocket.
North Korea had notified United Nations agencies in advance that it intended to put an earth observation satellite into orbit.
The launch was condemned by Japan, South Korea and the United States, amid fears the North is developing nuclear weapons capable of reaching the US mainland.
Mr McCully said the launch went against the UN Security Council resolutions demanding that North Korea cease any launches using ballistic missile technology.
He said the government would work with other Security Council members on an appropriate response to the launch.
An emergency meeting of the council has been convened tomorrow morning.
South Korea says it is to begin discussing with the US the deployment of a missile defence system.
Senior defence official Ryu Je-Seung said if the THAAD missile system - considered one of the most advanced in the world - were deployed it would be only to counter the threat from the North.
The North insists its space programme is purely scientific in nature but the US, South Korea and even ally China say the rocket launches are aimed at developing an inter-continental ballistic missile capable of striking the US.
North Korea provoked international criticism earlier this year with a fourth nuclear bomb test on 6 January.
South Korean analysts had speculated that the North might carry out the launch ahead of 16 February, the birthday of the late North Korean dictator Kim Jong Il.
UN Security Council resolutions ban the state from carrying out any nuclear or ballistic missile tests.
In a statement, the North Korean National Aerospace Development Administration said earth observation satellite Kwangmyongsong-4 had entered orbit about 10 minutes after lift-off from the Sohae space centre in North Phyongan province.
Announcing the launch on state TV, a newsreader said it had been ordered by North Korea's leader Kim Jong-un and said the country planned to launch more satellites in the future.
"The fascinating vapour of Juche satellite trailing in the clear and blue sky in spring of February on the threshold of the Day of the Shining Star,'' was how the launch was described.
South Korean Defence Ministry spokesman Moon Sang Gyun said a warship had detected the launch at 09:31 (00:31 GMT).
US National Security Adviser Susan Rice said North Korea's use of ballistic missile technology was "yet another destabilising and provocative action".
"North Korea's missile and nuclear weapons programs represent serious threats to our interests - including the security of some of our closest allies," she said in a statement.
Contenders for the Republican ticket in the US presidential election this year were asked for their reaction during a debate in New Hampshire.
Donald Trump said he would work with China to resolve the North Korea nuclear issue: "I would get on with China. Let China solve that problem. They can do it quickly and surgically. That's what we should do with North Korea."
North Korea's rocket launches
- February 2016: Launch of rocket reportedly carrying satellite
- May 2015: North Korea announces it has successfully tested a submarine-launched missile for the first time, but scepticism is then poured on the claim
- December 2012: North Korea launches three-stage rocket, says it successfully put a satellite into orbit; US defence officials confirm object in orbit
- April 2012: Three-stage rocket explodes just after take-off, falls into sea
- April 2009: Three-stage rocket launched; North Korea says it was a success, US says it failed and fell into the sea
- July 2006: North Korea test-fires a long-range Taepodong-2 missile; US said it failed shortly after take-off
- BBC / RNZ