People keep a lookout at the mouth of a river after tsunami advisories triggered by a 7.4-magnitude earthquake were issued, in Iwaki, Fukushima prefecture, Japan, on Nov 22, 2016. [Photo/Agencies]

TOKYO - An earthquake with a preliminary magnitude of 7.4 struck northeastern Japan's Fukushima on Tuesday, the weather agency said, while tsunami waves were observed in the area and some people were injured.

The 5:59 am local time quake registered lower 5 on the Japanese seismic scale of 7 in northeastern Fukushima prefecture, the Japan Meteorological Agency (JMA) said.

Tsunami warning for northeastern prefectures of Miyagi and Fukushima was downgraded to advisory at 9:46 am by the JMA, with the four prefectures of Miyagi, Fukushima, Iwate and Ibaraki given tsunami advisory at present.

At 8:03 am, 1.4-meter tsunami were observed at Sendai port in northeastern Miyagi prefecture, following the first wave of tsunami was observed at coastline 20 km east of Iwaki city in Fukushima prefecture.

Earlier in the morning, the weather agency warned of further tidal waves of up to 3 meters for Fukushima and 1 meter for other parts of the coastline facing the Pacific.

Tidal waves of 0.3-1.4 meters have been observed Tuesday morning at Onahama port and Soma port in Fukushima prefecture, Ofunato port and Kuji port in northeastern Iwate prefecture, Sendai port and Ishinomaki Ayukawa in northeastern Miyagi prefecture, Oarai port in eastern Ibaraki prefecture, and Katsuura in eastern Chiba prefecture.

Some persons were slightly injured in Fukushima and Sentai, including one struck by falling tableware at home and another cut by broken glass at a nursing home.

The epicenter of the quake was at a latitude of 37.3 degrees north and a longitude of 141.6 degrees east and occurred at depth of 30 km, said the weather agency.

The temblor was centered in waters offshore of northeastern Fukushima prefecture which borders the Pacific Ocean and is to the northeast of the nation's capital city of Tokyo.

The jolt, centered in the Fukushima, could be felt in central Tokyo and also shook other northeastern Japanese prefectures including Tochigi and Ibaraki.