Two New Zealand military aircraft, stocked with emergency relief supplies, took off for Tonga on Tuesday afternoon.
A C130 Hercules plane is carrying family hygiene kits, shelter kits, jerry cans and tarpaulins, which will be distributed to those whose homes were destroyed in Cyclone Gita.
The other, an NZDF P3K Orion, is carrying out a reconnasisance flight to survey the damage.
That's in addition to the New Zealand Government's offer to donate $750,000 to relief efforts.
A 10-person New Zealand government team is on board the plane. They will support the New Zealand High Commission in assessing "emergency needs and respond to requests from the Government of Tonga", the Government says.
The plane is carrying 500 family hygiene kits, 200 shelter tool kits, 2300 10-litre collapsible water containers and 1000 tarpaulins.
Cyclone Gita ravaged the main island of Tonga - Tongatapu - as well as satellite island 'Eua on Monday night. It's been called the worst storm in decades.
Winds reached up to 260km/hr during the night and many buildings have been destroyed. Among those structures levelled in the storm is Tonga's distinctive red-and-white parliament building.
"Initial assessments indicate there has been extensive damage to homes in Nuku'alofa and some damage to commercial buildings," Foreign Affairs Minister Winston Peters said on Tuesday afternoon.
"About 5700 people sought shelter in evacuation centres overnight and it is expected these numbers will increase substantially tonight."