Australian, Canadian and US warships are heading to the New Zealand town of Kaikoura to help with evacuations after a series of powerful earthquakes.
Two people were killed when two simultaneous quakes hit near Christchurch on Monday morning, followed by thousands of aftershocks.
Thousands were cut off in Kaikoura after roads and infrastructure were badly damaged.
Many were tourists visiting the popular whale-watching destination.
Helicopters began airlifting people from Kaikoura on Tuesday, after landslides cut off road and rail links. Power and water supplies have also been disrupted.
New Zealand's HMNZS Canterbury is already in operation off the coast, and will be joined later on Wednesday by Canada's HMC Vancouver, Australia's HMAS Darwin and the US destroyer USS Sampson.
The USS Sampson is the first US warship to visit New Zealand in 30 years.
The foreign warships had been destined for Auckland to take part in 75th anniversary celebrations for the New Zealand navy but diverted to help with the recovery effort.
New Zealand defence minister Gerry Brownlee said the offer of assistance was ‘heartening’, and that Japan and Singapore had also offered help.
Meanwhile the cleanup is continuing in Christchurch and the capital, Wellington. Some streets remain cordoned off while safety checks are carried out on damaged buildings.
Officials say there have been up to 100,000 landslides across the affected region.
New Zealand's government-funded earthquake monitoring service Geonet said Monday's quake - actually two at the same time - had a magnitude of 7.5, making it the largest in the quake-prone country since 2009.
The US geological survey placed it at 7.8.
Geonet said there had been more than 1,700 quakes and aftershocks since Monday, and that further tremors were highly likely.
New Zealand lies on the Ring of Fire, the fault line that circles virtually the entire Pacific Rim bringing frequent quakes and volcanic eruptions.
Christchurch is still recovering from a 2011 earthquake that killed 185 people and destroyed the city centre.
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