The new quake struck the Kanto region in eastern Japan at 11:19 am local time and was centred about 79 km below the ground in southern Ibaraki prefecture, according to the country's Meteorological Agency.

There were no initial reports of damage from the tremor, which shook buildings in Tokyo as well, more than a month after a monster magnitude-9 quake and tsunami left nearly 30,000 people dead or unaccounted for.

The quake came hours after the government's nuclear safety agency asked operators of 13 nuclear plants across the country to step up their preparation to avoid outages and other damage to the facilities in the event of an earthquake.

Last month's twin disaster has caused massive damage to the Fukushima nuclear plant, which continues to leak high radiation into the air and sea.

Tokyo Electric Power Company (TEPCO), the embattled operator of the plant, said the level of highly radioactive water in a tunnel of the No.2 reactor has been rising, national broadcaster NHK reported.

Contaminated water in the plant's facilities is hampering efforts to restore reactor cooling systems. Leakages of such water into the sea and the ground are also raising concern.
TEPCO transferred about 660 tonnes of wastewater from the tunnel to a condenser in a turbine building on Wednesday. This lowered the water level in the tunnel by 8 cm but it began rising again, exceeding the previous level by 2.5 cm this morning.

On TEPCO's announcement that it would provide USD 12,000 in provisional compensation to each of 50,000 affected households near the plant, some of the evacuees said the firm should have made the decision earlier.

A 70-year-old woman was quoted as saying that the money will be helpful at least for a while, but will certainly not be enough if their evacuation is prolonged. Another tsunami-ravaged prefecture of Miyagi will launch free radiation measuring next Monday for locally assembled industrial goods to combat "groundless and harmful rumours" about them, amid the ongoing nuclear crisis in the neighbouring Fukushima region, Kyodo news agency reported.

Subject to the move running through June will be primarily electronic components and machinery, local officials were quoted as saying, adding manufacturers need to make appointments with the prefecture's Industrial Technology Institute for checkups, including issuing documents for submission to clients.

The move comes as some local firms have faced demands from business partners to check their products for radioactivity.

"Machinery is basically assembled indoors and there must be little to be worried about. But we have to do this as (the companies) were asked (to have their products checked)," one of the prefectural officials was quoted as saying.

In Washington, the Group of 20 financial chiefs expressed solidarity with the Japanese people over the devastating March 11 quake and tsunami, pledging to offer any support needed by the crisis-hit country.

With the crisis at the troubled Fukushima plant continuing, the G-20 warned that Japan's economic downturn is a downside risk to the global economy. Meanwhile, 'Asahi Shimbun' newspaper reported that a secret plan to dismantle TEPCO is circulating within the government.

The proposal envisages the passing of a special measures law that would put the company under close government supervision before eventually bankrupting it and completely restructuring its remnants, it said.

There are also proposals to smash the company's powerful influence on politicians and the mass media and force executives to give all their pay and severance settlements to victims of the earthquake, the report said.