Prime Minister Jacinda Ardern says New Zealand joins its international partners in condemnation of Russia's attack on Ukraine and has immediately taken a range of measures against the Russian government.

Russian President Vladimir Putin declared war on Ukraine and launched a full-scale land, sea and air attack on the country overnight on Thursday local time.

Putin said his goal was the "demilitarisation and denazification" of Ukraine, but US President Joe Biden has asserted the evidence clearly shows Russia is the aggressor and it has no evidence for its justifications.

New Zealand has joined with the UN in launching economic sanctions against Russia.

Ardern says Russia began a "military offensive and an illegal invasion" of Ukraine yesterday, New Zealand time.

"The UK's Ministry of Defence communicated this morning that more than 80 strikes have been carried out against Ukrainian targets and that Russian ground forces are advancing across the border on at least three axis from north and northeast, and south from Crimea," the prime minister says.

"There are reports of attacks in a range of locations around Ukraine, including heavy shelling in eastern Ukraine and fighting in some areas, including around airports and other targets of strategic importance."

She says New Zealand joins its international partners in condemnation of the attack and has immediately taken a range of measures against the Russian government.

"By choosing to pursue this entirely avoidable path, an unthinkable number of innocent lives could be lost because of Russia's decision," she says.

New Zealand calls on Russia to do what is right and immediately cease military operations, and permanently withdraw to avoid a "catastrophic and pointless loss of innocent life", she says.

The invasion poses a significant threat to peace and security in the region and will trigger a humanitarian and refugee crisis, she says.

Russia has demonstrated a disregard for diplomacy and efforts to avoid conflict in the lead-up to the attack, she says, and "must now face the consequences of their decision to invade".

As a permanent UN Security Council member, Russia has "displayed a flagrant disregard for international law and abdicated their responsibility to uphold global peace and security" and now must face the consequences, Ardern says.

New Zealand has immediately imposed measures in response which include targeted travel bans against Russian officials and other individuals associated with the invasion. They will be banned from obtaining visas to enter or transit New Zealand.

Secondly, this country is prohibiting the export of goods to Russian military and security forces.

"While exports from New Zealand under this category are limited, a blanket ban is a significant step as it removes the ability for exporters to apply for a permit and sends a clear signal of support to Ukraine," she says.

Finally, New Zealand has suspended bilateral ministry consultations until further notice.

Ardern says there will be a significant cost imposed on Russia for its actions. New Zealand will also consider humanitarian response options, she says.

"Finally our thoughts today are with the people in Ukraine affected by this conflict. Decades of peace and security in the region have been undermined.

"The institutions built to avoid conflict have been threatened and we stand resolute in our support for those who now bear the brunt of Russia's decisions."

She again calls for Russia to cease military actions and return to diplomatic negotiations to resolve the conflict.

During questions from journalists, Ardern says New Zealand is not constrained by being unable to launch autonomous sanctions.

"There are additional measures that we can take. Obviously already you'll see those targeted travel bans, we do have the ability to extend those as required and as those involved with this activity grows.

"We also have the ability to continue to restrict the amount of diplomatic engagement that we have ... and obviously the autonomous sanction regimes that have been proposed in the past don't for instance cover situations of human rights violations."

Ardern admits there are some limitations on economic sanctions New Zealand can impose, but the government continues to get advice from the Ministry of Foreign Affairs about the tools that can be used and "we want them all to be on the table".

The measures New Zealand has imposed are limited but send a very clear message.

"What this does say is that there's no ability to apply or seek to export ... this is a blanket ban," she says.

She says New Zealand's response is very much in line with other countries, and the world is sending a very clear message to Russia that what they are doing is wrong " and they will face the condemnation of the world".

"One of the things that does stand out currently with this conflict is just the degree to which there is unity, unity of voice, that what is happening here - the blatant breach of international law, a rules based order - how that stands in the face of everything that countries have worked so hard for in the wake of World War II."

She says the messages shared in unity send a strong message and it is important New Zealand shares in that.

Some differences compared to other countries is New Zealand has not frozen assets, "but again that is an act that in some countries would have a much greater effect".

"What we have here is a member of the security council who is now blatantly undermining our international rules-based order."

She says she has not removed the idea that an autonomous sanctions regime may be introduced in future.

She says historically New Zealand's imports of Russian oil have been limited "about 20 percent", and Z Energy for example has not purchased any in the last six months.

"Our fuel supply tends to be dominated by Middle East and Asia."

She says New Zealand has security of supply and what is happening won't affect that, but an effect on international markets due to the role Russia plays - not just fuel but also wheat - can be expected.

She says about 40 New Zealanders have been recorded as being in the region.

New Zealand issued advice to leave the area before the invasion began, and has supported some individuals to leave. Commercial options to depart have since reduced, and New Zealand has a consular team in southeastern Poland, which is where those seeking to exit Ukraine are most likely to go.

At this stage it's too early to say what New Zealand's humanitarian support and ability to take refugees will be, she says.

Asked what makes her think New Zealand and other countries' interventions will have any effect on Russia, Ardern says "the alternative of doing nothing just can't stand".

She says there have always been challenges to the rules-based international order, but this is the blatant use of military might and violence that will take innocent lives.

- RNZ