A strong earth quake with a magnitude of 6.2 in the Richter scale hit the Japanese capital Tokyo, Monday, causing the buildings to sway for more than 30 seconds, national broadcaster NHK reported. The broadcaster said there was no alert issued for tsunami.

"An earthquake occurred at about 4:23 p.m. today," an AFP report quoting the Japan Meteorological Agency reported. "Its focus was in the north of Tochigi prefecture. Its depth is about 10 kilometers and its magnitude is estimated at 6.2," it added.

A few minutes later, a 4.7-magnitude aftershock was recorded, The Daily Yomiuri reported. There were no immediate reports of casualties and injuries.

Tokyo Electric Power Co. said there were no reports of irregularities at its Fukushima Daiichi nuclear plant in north-eastern Japan or at its other nuclear facilities, Reuters reported.

More details are awaited.