Tokyo, March 21 (DPA) Japanese military and a fire department showered more water onto an overheating reactor early Monday at a troubled nuclear plant in northeast Japan, trying for a fifth day with hoses to avert a potential meltdown.

Thirteen Japanese military trucks spent about one and a half hours in the morning spraying a total of 90 tonnes of water at the spent fuel pool of reactor No.4 at the Fukushima nuclear power station, 240 km northeast of Tokyo, public broadcaster NHK reported, citing the defence ministry.

The plant's cooling system was damaged by the March 11 earthquake and tsunami.

Overnight, a Tokyo fire department doused reactor No.3 for hours. That effort lasted until 4 a.m. (1900 GMT Sunday).

The operation was working, as the temperatures of the pools at all six reactor units fell below 100 degrees Celsius, Defence Minister Toshimi Kitazawa said.

Two armoured vehicles are to be mobilised Monday to remove rubble at the plant, which has hampered the operation to cool down the reactors.

Off-site electricity reached the buildings of reactors No.2 and No.5 at the plant, a key step to cool the reactors, news reports said, citing the plant's operator Tokyo Electric Power Corp (TEPCO).

The news was overshadowed, however, by fresh reports of spinach and milk being contaminated by radiation in the prefecture that is home to the stricken plant and other areas.

The government will decide by Monday whether it needs to regulate farm products near the Fukushima nuclear power plant, Chief Cabinet Secretary Yukio Edano said at a news conference Sunday.