TOKYO - An earthquake with a preliminary magnitude of 6.6 jolted northeast Japan on Saturday, shaking buildings in the capital of Tokyo and raising the possibility of landsides, although no tsunami alert was issued.

The earthquake struck off the coast of northeastern Miyagi prefecture at a depth of 60 kilometres (37 miles), the Japan Meteorological Agency said. It warned about possible landslides. There were no immediate reports of injuries.

Buildings shook in Tokyo, the capital, some 400 kilometres away and public broadcaster NHK showed footage of a building shaking strongly in the northeastern city of Sendai.

At the devastated Fukushima Daiichi nuclear plant, which was wrecked by a massive earthquake in northeast Japan a decade ago, operator Tokyo Electric Power 9501.T said there were no issues. Likewise there were no issues at the Fukushima Daini facility just to the south.

Nearer to the epicentre, there were no issues at the Onagawa nuclear station, according to operator Tohoku Electric Power Co Inc 9506.T .

Bullet train services throughout northern Japan were suspended, with no schedule for restarting operations as checks on passengers and trains were made, an East Japan Railway Co 9020.T representative said.

The coast off northeast Japan has been hit by multiple earthquakes in recent months, including a magnitude 7.2 quake in March and a similar sized one in February. The magnitude 9 quake in 2011 was one of the strongest earthquakes on record.

Eneos Holdings Inc, 5020.T Japan's biggest refining company, said its Sendai refinery, also located close to the epicentre, automatically shut down as the quake struck. Engineers were making checks after confirming there were no injuries, it said.

The 145,000-bpd refinery had only restarted in April after being damaged by the February earthquake. That quake knocked out one fifth of Japan's refining capacity. 

(Reporting by Aaron Sheldrick and Kevin Buckland; editing by Stephen Coates, David Dolan and Richard Pullin) ((aaron.sheldrick@thomsonreuters.com; 81-80-2677-4134;))