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. Media reports say the ships could be dispatched as early as March.

"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.

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

Japan's plan follows a U.N. Security Council decision authorizing 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. The U.N. authorization was extended for another year in early December.

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 have 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 and limits the country's warships to protect only Japanese vessels and their crew. 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.

Officials are considering sending warships and aircraft but details are yet to be finalized, a ministry official said later Wednesday on condition of anonymity, citing department policy.

Japan's Yomiuri newspaper reported that two destroyers and two patrolling helicopters will be dispatched to escort commercial Japanese vessels. The paper did not give a source for the information.

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.