WELLINGTON -- New Zealand disaster response authority issued a tsunami warning for all southern coastal areas of the country after a 6.6-magnitude earthquake struck in the wee hours on Monday.

The Ministry of Civil Defense and Emergency Management said in a statement that a tsunami is possible.

"The first wave activity may not be the most significant. Tsunami activity will continue for several hours and the threat must be regarded as real until this warning is cancelled," it said.

The epicenter of the quake is located at 15 km southeast of Hanmer Spring, a hot spring tourist town some 130 northwest of Christchurch, the biggest city of south island.