A mammoth relief mission is swinging into action in north-east Japan, a day after it was struck by a devastating tsunami, claiming hundreds of lives. The disaster was triggered by an 8.9-magnitude earthquake, the country's most powerful since records began. The government has warned there could be a radioactive leak at a nuclear power reactor shut down by the quake. Prime Minister Naoto Kan is likely to hold an emergency cabinet meeting today, before visiting the disaster zone by helicopter. The country's military has mobilised thousands of troops, 300 planes and 40 ships for the relief effort.The quake triggered a tsunami up to 10 metres, with waves of 7 metres battering the Japanese coast. A muddy torrent of water swept cars and homes far inland, turning residential areas and paddy fields into a lagoon of debris-filled sea water. One of the worst-hit areas was the port city of Sendai, in Miyagi prefecture, where up to 300 bodies have been found in one ward alone.