The government will submit an antipiracy bill to the Diet that would allow foreign security contractors aboard Japanese flag-bearing vessels to carry firearms while in waters off Somalia and elsewhere, sources close to the issue said Sunday.

Vessels registered in Japan are prohibited from carrying private armed guards, under the Sword and Firearm Control Law.

Under the bill drafted by the Land, Infrastructure, Transport and Tourism Ministry, warning shots will be permitted but firing at people will not, unless in self-defense, the sources said.

Ship owners will be required to disclose details on their equipment and security plans as well as the capabilities of the security staff on board before receiving government approval. They also will be required to submit an application for every journey, according to the ministry’s plan.

The legislation would be limited to vessels sailing in piracy-infested waters, such as near Somalia or in the Arabian Sea.

The ministry said 237 cases of piracy were reported around Somalia in 2011, a five-fold increase from 2007.

Many of the pirates are believed to be Somalian hijackers bent on taking the vessels and crew hostage for ransom. In many cases, they are armed with automatic weapons and rocket launchers, they said.

Although many countries, including Japan, have deployed naval forces to protect private ships from piracy, shipping companies say they are being increasingly forced to come up with their own self-defense measures.

Major shipping line Kawasaki Kisen Kaisha Ltd. said its vessels have specially shelters the crew can use to protect themselves until help arrives. But an official of the company said the increasing number of attacks might prevent Japanese ships from operating off Somalia unless defensive measures can be improved.