The government approved emergency plans Friday for 21 prefectures to protect the public in the event of an attack.

The move stems from a set of 10 laws enacted in 2003 and 2004. They are the first pieces of postwar legislation to address measures that can be taken in the event of a national emergency.

The are now 23 prefectures with emergency plans. Fukui and Tottori finalized their plans last year. The rest of the prefectural governments have until the end of March to submit their plans.

The individual plans are based on a model from the central government. Each prefecture must take into consideration such factors as its land features, climate, population density and key installations, including nuclear plants.

Saitama lists measures for specific scenarios, including the "spraying of sarin nerve gas in a terminal station" and the "bombing of an expressway."

Osaka tells its residents to take shelter immediately in the event of a land attack and then evacuate to a safer place. In a nuclear attack, it says people should move upwind.

The plan for Kyoto includes steps to protect cultural assets and evacuate tourists, while Shimane, Yamaguchi and other prefectures with remote islands describe how to evacuate residents by boat.

Hokkaido and three prefectures in the Tohoku region address the issues of heating and snow removal, while others, including Ibaraki, Ishikawa and Saga, outline how to deal with their nuclear facilities.

In June 2004, the Diet passed seven laws to complete its package of war contingency legislation that began a year earlier to address concerns of an attack.

Two of those seven laws are to help facilitate U.S. military operations in the event of an attack or imminent attack, and to enable Tokyo to supply provisions to the U.S. forces in an emergency.

The other five address measures to be taken to evacuate and protect the public, to raid ships in Japanese and surrounding international waters, give priority to military use of public facilities and to ensure the proper treatment of prisoners of war.