Snapshot: Japan's nuclear crisis

Firemen put out fire at a devastated area hit by earthquake and tsunami in Kesennuma, Miyagi Prefecture in northern Japan, March 15, 2011.

TOKYO (Reuters) - Following are main developments after a massive earthquake and tsunami devastated northeast Japan and crippled a nuclear power station, raising the risk of uncontrolled radiation.

* Engineers work through the night to lay a 1.5 km (one mile) electricity cable to the crippled Fukushima Daiichi nuclear complex in the hope of restarting pumps needed to pour cold water on overheating fuel rods.

- Military helicopters and fire trucks had earlier poured water on the overheating plant.

- Engineers hope to use power from the main grid to restart water pumps to cool reactor No. 2, which does not house spent fuel rods considered the biggest risk of spewing radioactivity into the atmosphere.

- A water cannon also douses No. 3 reactor, the top priority for authorities with plutonium fuel inside. Smoke and steam had been escaping from the unit, indicating water evaporating from the cooling pool. Pressure had been rising.

- United States sends aircraft to fly out nationals from Japan, authorizes voluntary departure of family members of diplomatic staff.

- An official at the Nuclear and Industrial Safety Administration says three of the plant's six reactors - Nos. 1, 5 and 6 - are relatively stable. The official could not confirm whether water was covering spent fuel rods in reactor No. 4. - Top U.S. nuclear regulator earlier said no water was left in No. 4 reactor cooling pool, radiation levels extremely high.

* The head of the U.N. nuclear watchdog, the IAEA, is on his way to Japan. He said earlier core damage at reactors 1, 2 and 3 of the plant was confirmed, but reactor vessels seemed intact.

- Eighteen months before the crisis, U.S. diplomats had lambasted the IAEA's safety chief for incompetence, especially when it came to the nuclear power industry in his native Japan, according to cables sent by the U.S. embassy in Vienna to Washington. The cables, obtained by WikiLeaks and reviewed by Reuters, singled out Tomihiro Taniuchi, until last year the IAEA's head of safety and security.

- Japan PM Kan briefs President Barack Obama. U.S. to fly a drone over the complex to assess the emergency. Australia again urges nationals in Tokyo and eight prefectures to consider leaving Japan. That warning was because of infrastructure problems, not the fear of radiation.

- Tokyo is safe for international travelers, the Japanese Red Cross says, but airlines pull in extra, larger aircraft to help thousands of people leave and some begin screening aircraft, passengers and crew for radiation.

* The Pentagon says it will allow all dependents of U.S. military personnel to leave Japan's Honshu island while Homeland Security Secretary Janet Napolitano says passengers and cargo arriving in the United States from Japan would be checked for radiation.

- Economics Minister Kaoru Yosanu tells Reuters Japanese markets are not sufficiently destabilized to warrant joint G7 currency intervention or government purchases of shares.

- Yen jumps 4 percent against the dollar, the Nikkei down 1.4 percent. Officials blames yen spike on speculators. Bank of Japan offers to inject a further 6 trillion yen ($74 billion) into the banking system.

- Estimates of losses to Japanese output from damage to buildings, production and consumer activity range from 10 to 16 trillion yen ($125-$200 billion), up to 1 times the economic losses from the 1995 Kobe earthquake.

- Nuclear crisis diverts attention from the tens of thousands affected by last week's earthquake and tsunami. About 850,000 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)