Wellington, Sep 2 (IANS) : A tsunami warning was issued after an earthquake, measuring 7.1 on the Richter Scale, hit Zealand's North Island on Friday, the media reported.

The quake hit around 100 km northeast of the East Cape settlement of Te Araroa, at a depth of 55 km, The New Zealand Herald reported.

A potential tsunami threat was upgraded to a warning by Civil Defence officials shortly after 6 a.m. (local time) after the quake hit at 4.37 a.m.

"Tsunami activity will continue for several hours and the threat must be regarded as real until this warning is cancelled," Civil Defence said in a statement.

The people have been asked to listen to radio and TV for further updates and follow the instructions of their local Civil Defence authorities.

The warning covers the East coast of the North Island, including Auckland, Waikato and Bay of Plenty and the upper South Island.

The quake lasted for almost a minute and was felt across much of the North Island.

The quake was followed by several moderate-sized aftershocks, including a 5.6-magnitude jolt at 5.01 a.m., and a 4.6-magnitude quake at 5.03 a.m.