UPDATE 1-KEY POINTS-Official update on Japan nuclear crisis

TOKYO, March 15 (Reuters) - The following are key points from the latest briefings given on Tuesday by the Japanese government and nuclear power generator Tokyo Electric Power about the nuclear crisis.

* Radiation levels at the quake-stricken Fukushima Daiichi complex have varied wildly, with a reading of 11,930 microsieverts at the main gate of the plant at 0000 GMT, up from 596 microsieverts as of 0630 GMT.

* Elsewhere at the plant, levels reached as high as 400,000 microsieverts an hour (or 400 millisieverts an hour).

* The government gave no update on the status of a steel container surrounding the core of the plant's No.2 reactor, deemed by observers as most at risk of a meltdown.

* An explosion on Tuesday at the No.2 reactor had caused some damage to its suppression pool, which helps to cool and trap the majority of cesium, iodine, strontium in its water.

* Later, there was a fire and explosion at the complex's No. 4 reactor and this is likely to have contributed to rising radiation levels.

* The No. 4 reactor had been shut down for maintenance ahead of the quake, but a spent-fuel cooling pool associated with that reactor caught fire, causing the explosion.

* The No.4 reactor's cooling pool, where spent nuclear fuel is stored, may be boiling and the water level may be falling.

* Radioactivity at the cooling pool is high and Tokyo Electric cannot make checks at the site or determine what has burned.

* Radiation leakage from complex is likely to spread after a fresh explosion at the plant. (Reporting by Shinichi Saoshiro and Osamu Tsukimori; Editing by Mark Bendeich)