The Tonga Red Cross was among a group of organisations that was preparing to fly out to the area with supplies and aid.
The Ministry of Foreign Affairs and Trade said New Zealand had deployed a P3 Orion to assist Tonga's government with aerial assessment of damage.
Foreign Affairs Minister Murray McCully today announced that New Zealand would make $50,000 immediately available to respond to specific requests for assistance.
``Our thoughts are with the people of Tonga as they begin to come to terms with the damaged caused by this cyclone.''
Early reports suggested damage to buildings in parts of Ha'apai, limited communications and power outages, he said.
More details would become available as Tongan authorities made assessments.
Further support would be considered as the full extent of the damage became clear and Tonga's government determined its priority response areas, Mr McCully said.
New Zealanders in Tonga were advised to follow the advice of the local authorities (including any evacuation orders), seek suitable shelter, monitor local media for updates, and keep friends and family in New Zealand informed of their well-being.
If they required consular advice they should contact the New Zealand High Commission in Nuku' alofa.
An MFAT spokeswoman said New Zealand was in close contact with Tongan emergency management authorities and stood ready to help if requested.
There were 114 New Zealanders registered with the ministry as being in Tonga.
Oxfam is accepting donations for its rapid response emergency fund online at www.oxfam.org.nz, by phone 0800 600 700, or text HELP to 4847 for an automatic $3 donation.