White steam-like vapour was seen rising from one reactor and what looked like white hazy smoke from another, 11 days after a monster 14-metre (46-foot) tsunami knocked out the plant's cooling systems and backup generators.

Plant staff and technicians, firefighters and military personnel were struggling to prevent a full meltdown at the seaside plant but spikes in radiation levels have at times forced the crews to suspend work.

Higher than normal levels of radiation have been detected in some farm produce from regions around the plant, as well as in sea water and tap water in Tokyo, forcing authorities to suspend shipments of milk and some vegetables.

Prime Minister Naoto Kan's office moved to reassure consumers Tuesday that no seafood from Fukushima prefecture had entered the market since the quake.

Fears of a full-scale nuclear disaster at the Fukushima No. 1 plant, which lies just 250 kilometres from the greater Tokyo area and its 30 million inhabitants, have in many ways overshadowed the twin natural disaster, which has now left 8,805 people dead and a further 12,664 listed as missing.

AFP