A 7.1 magnitude earthquake jolted the east coast of New Zealand at 4:37 am (2107 IST) on 2 September, followed by several aftershocks of nearly 6.0 magnitude.
According to reports, a small tsunami of 30-centimetre was generated but no significant damage or injuries took place.
"The greatest wave height has already occurred, further waves are anticipated to be up to 20 centimetres," the Civil Defence organisation, which is responsible for national emergency management, was quoted by an international news agency.
"Areas under 'marine and beach threat' can expect unusually strong currents and unpredictable water flows near the shore. This means a threat to beach, harbour, estuary and small boat activities."
However, despite the power of the temblor, East Coast Civil Defence information officer Sheridan Gundry told Radio New Zealand the impact was minimal.
"We haven't heard any reports of injuries or damage at all," East Coast Civil Defence information officer Sheridan Gundry told Radio New Zealand.
"There was power out in a few places but we've been let off pretty lightly as far as damage goes," she was quoted in the report.
The tsunami warning covered the East Coast of the North Island and the upper South Island.
It struck at 4:37am (2107 IST) and was centred 167 kilometres from the nearest main town, Gisborne, which has a population of around 45,000.
In New Zealand, where earthquakes are common, Civil Defence regularly holds practice drills for coastal residents so they know how to react in an emergency.
In February 2011, a 6.3 earthquake left 185 people dead in the South Island city of Christhurch.