A powerful earthquake struck northeastern Japan on Tuesday morning, briefly disrupting nuclear fuel cooling functions at the Fukushima No. 2 power plant and generating tsunami of over 1 meter in the region that was devastated by the Great East Japan Earthquake, tsunami and nuclear disaster five years ago.

The 5:59 a.m. quake with a preliminary magnitude of 7.4 is believed to be an aftershock of the March 2011 mega-quake, the Meteorological Agency said.

It was the first quake with a magnitude of 7 or bigger to hit Japan since July 2014. The agency warned that there may be similar-scale quakes for around a week.