Thousands of New Zealanders on the east coast of the country's North Island evacuated to the higher ground today, and its biggest city was put on alert after three offshore earthquakes in less than eight hours triggered tsunami sirens and warnings.

Workers, students and residents in areas like Northland and Bay of Plenty, on the northern coast near Auckland, were assisted by civil defence officials as authorities said tsunami waves could reach three metres (10 feet) above tide levels...