5.8-magnitude quake strikes, no tsunami alert

An offshore quake struck 140 kilometres (87 miles) northeast of Tokyo Monday morning, shaking tall buildings in Japan's capital, but authorities did not issue a tsunami alert.

There were no immediate reports of damage or casualties.

The quake off coastal Ibaraki prefecture -- one of many aftershocks since Friday's massive 8.9 quake -- had a 5.8-magnitude, said the US Geological Survey, which said the quake struck at a depth of 18 kilometres.