Japan's defense minister Wednesday ordered the dispatch of ships to fight pirates off the shores of Somalia, joining countries ranging from the United States to Iran to China in the battle against the outlaws.

Defense Minister Yasukazu Hamada did not say how many Japanese ships would be sent or when, and said his dispatch order was an interim measure until parliament passes a formal law outlining the ships' activities in their mission against piracy.

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"The pirates' activities off the Somali coast are a major threat not only to Japan but also to international society and it is a problem that we must deal with urgently," Hamada said.

Hamada ordered the government to study the size of troops needed and report back to him.

Japan made the decision in line with a U.N. Security Council decision in early December extended for another year its authorization for countries to enter Somalia's territorial waters, with advance notice, and use "all necessary means" to stop acts of piracy and armed robbery at sea.

Piracy has taken an increasing toll on international shipping, especially in the Gulf of Aden, one of the world's busiest sea lanes. Pirates made an estimated $30 million hijacking ships for ransom last year, seizing more than 40 vessels off Somalia's 1,880-mile coastline.

Japan's government said no Japanese ships have been hijacked, but pirates fired at three Japanese vessels. No one was injured.

The order Wednesday follows months of debate in Japan's parliament.

The activities of Japan's military are highly restricted by Japan's post World War II constitution, which limits Japan to conducting only defensive military operations. Ruling party members have argued that battling pirates should be seen as fighting crime on the high seas, not strictly as a military operation.

More than a dozen warships are guarding Somalia's waters. Countries including Britain, Iran, America, France and Germany have naval forces off the Somali coast or on their way there. China and South Korea have also ordered the dispatch of warships to protect their vessels and crews from pirates.

Somalia, a nation of about 8 million people, has not had a functioning government since warlords overthrew a dictator in 1991 and then turned on each other. The current government, formed in 2004 with the help of the U.N. and backed by Ethiopia, has failed to protect citizens while it battles a growing Islamist insurgency.