A 7.4 magnitude earthquake off Japan's Fukushima and Miyagi prefectures has sparked tsunami waves of more than 1m. There were no reports of deaths or serious injuries several hours after the quake hit at 5:59am (20:59 GMT Monday). Television footage showed ships moving out to sea from harbours as tsunami warning signals wailed, after warnings of waves of up to 3 metres (10 feet) were issued. All Japan's nuclear power plants on the coast threatened by the tsunami are shut down in the wake of the March 2011 disaster, which knocked out Tokyo Electric Power Co's Fukushima Daiichi nuclear plant, spilling radiation into the air and sea. A spokeswoman for Tokyo Electric Power, known as Tepco, said the cooling system for a storage pool for spent nuclear fuel at the reactor at its Fukushima Daini Plant had been halted. A spokesman said the cooling system had restarted soon after. Only two reactors are operating in Japan, both in the southwest. Even when in shutdown, nuclear plants need cooling systems operating to keep spent fuel cool.Officials have said there is no sign of damage to the plant this time.