The government is planning to allow foreign-registered oil tankers and other energy transporter ships operated by Japanese firms to fly the Japanese flag as a way to protect them from pirates, a transport ministry official said Sunday.

Many of the ships operated by Japanese shipping companies are registered in Panama and elsewhere, where lower taxes are imposed on such vessels than in Japan.

Their flags reflect the country where they are registered. However, swift responses during pirate attacks or accidents cannot be expected from the countries where the ships are registered.

The Land, Infrastructure and Transport Ministry is considering separating registration and ensigns so that, for instance, a foreign-registered oil tanker owned and run by a Japanese company could fly the Japanese flag and be protected by Japan, the official said.

Pirate attacks are common in the Strait of Malacca, a vital choke point.

The types of ships to be covered by the planned step will be determined later, according to the official. Legislation necessary to revise the Ships Law will be introduced to the Diet as early as next year.

After the revision, a change in ensign requires consent from the country of registration, but given that Britain, France, Germany and others have already been implementing similar measures, the ministry believes there would be no problems, the official said.

"It is imperative that ships under government responsibility and protection be increased so that imports of oil and other commodities will not be stopped," the official said.