Snapshot - Japan's nuclear crisis

* Exhausted engineers scrambled to fix a power cable to two reactors at a the crippled Fukushima Daiichi nuclear power station as they fought to prevent a deadly radiation release in the world's worst nuclear accident since the Chernobyl disaster.

- Japan's nuclear safety agency says cannot say if the quake-damaged nuclear reactors are under control.

* The U.N. atomic agency says conditions at the plant are grave but not deteriorating badly.

- Japanese engineers say entombing the plant with concrete and sand may be a last resort to prevent a catastrophic radiation leak, the method used at Chernobyl in Ukraine in 1986.

- For now, workers are dumping water to cool the most critical No.3 reactor and plan to run a power cable to reactors No.1 and 2 by Saturday to restart the water pumps needed to cool overheating fuel rods.

- Japan's nuclear agency says priority is to get water into spent fuel pools, particularly in reactor No. 3, which contains plutonium.

- The agency also raised the incident level at the stricken power plant to a 5 on a 1-7 scale. That would suggest a level of seriousness on par with the Three Mile Island nuclear accident in the United States in 1979. But it said there was no need to expand the evacuation area beyond 30 km at this point.

- The head of the U.S. Nuclear Regulatory Commission, Gregory Jaczko, says it could take weeks to cool the reactors. About 300 workers, wearing masks, goggles and protective suits are toiling in the radioactive wreckage.

- Japan's nuclear agency said the radiation level at the plant was as high as 20 millisieverts per hour. The limit for workers was 100 per hour.

- G7 industrialised countries agreed, after a teleconference of finance ministers, on concerted intervention, the first since 2000, to restrain the yen, hoping to calm global markets.

The U.S. dollar surges two yen as far as 81.83 yen, leaving behind a record low of 76.25 Thursday, after the Bank of Japan began to sell yen and other central banks agreed to intervene later. Japanese shares jump 2.72 percent, but were still down about 10 percent on the week.

- World Health Organisation believes the spread of radiation is localised and poses no immediate risk to human health. Millions in Tokyo remain indoors, though winds are likely to carry contaminated smoke or steam away over the Pacific Ocean.

- U.S. President Barack Obama says he has requested a comprehensive review of U.S. nuclear facilities, while maintaining backing for atomic energy.

- Airlines pull in extra, larger aircraft to help thousands of people leave. U.S. Homeland Security Secretary Janet Napolitano says passengers and cargo arriving from Japan will be checked for radiation. Other countries also begin screening.

- Nuclear crisis diverts attention from the tens of thousands affected by last week's earthquake and tsunami. About 320,000 households in the north without electricity in near-freezing weather. Death toll is expected to exceed 10,000.

(Tokyo bureau; Compiled by World Desk Asia)