Pirates fired rocket-propelled grenades and automatic weapons at Japanese, Greek and Hong Kong cargo ships off the coast of Somalia but fled after the ships took evasive maneuvers, officials said Monday.

No one was injured in the attacks, the latest to be reported in Somalia's pirate-infested waters.

Masami Suekado, a Japanese Transport Ministry official, said pirates in two small vessels approached the Jasmine Ace and fired several shots before fleeing. Bullets broke windows and hit the ceiling of the bridge.

Noel Choong, who heads the International Maritime Bureau's piracy reporting center in Kuala Lumpur, said the attack was one of three Sunday off southern Somalia, about 500 nautical miles from the coast.

In the other attacks, pirates in two small boats fired RPGs and machine guns for 30 minutes at a Hong Kong container ship but the vessel managed to escape by increasing speed and carrying out evasive maneuvers.

An hour later, the brigands fired at a Greek bulk carrier but aborted the attempt after the ship took anti-piracy measures, including evasive maneuvers, he said.

The Japanese cargo ship was attacked four hours after the Greek carrier.

"Fortunately no one was injured and killed. It is believed to be the same pirate group and it shows they are now operating in the southern part of Somalia," Choong said.

Atsuko Nakajima, a spokesman for Mitsui O.S.K Lines, which operates the Japanese ship, said 18 people — all from the Philippines — were aboard the ship, which was carrying a cargo of automobiles. Nakajima declined to give the ship's current location for security reasons.

Suekado said the 13,000-ton cargo ship zigzagged away and the pirates broke off their assault. The ship was heading toward Mombasa, in Kenya, when it was attacked.

Last year, 12 Japanese owned or operated ships were attacked in the area. This was the first strike on a Japanese operated ship there this year.

To help get control of the situation, two Japanese navy destroyers left earlier this month to join an international anti-piracy mission. The five-month deployment marks the first overseas policing action for Japan's military, which is limited by the country's post-World War II constitution to defensive missions.

They are expected to reach Somalia's coastal waters next month.

Japan's dispatch comes as more than a dozen warships from countries including Britain, the United States, France, China and Germany are guarding the region.

Authorities say marauding criminals in speedboats attacked more than 100 ships off Somalia's coast last year, including high-profile hijackings with multimillion-dollar ransom demands. There were roughly 10 times as many attacks in January and February 2009 as there were over the same period last year.

But while Somalia's pirates are keeping up their attacks in one of the world's most important shipping routes, they are finding it harder to seize vessels in recent months, according to the International Maritime Bureau.

The Bahrain-based U.S. 5th Fleet, which patrols the region, says the decline in the number of successful pirate attacks could be partly attributed to the increased number of warships in the area — between 15 and 20 at any one time.

Choong, however, said attacks have increased in recent weeks due to better weather, with pirates becoming more violent as their attempts continue to be foiled by the international naval coalition.

"Pirates are quite desperate now, so they will start firing to stop the ships and intimidate the captain," Choong said. The focus appears to be on the eastern and northern coast of Somalia, where there are fewer naval patrols, he said.

Forty ships have been attacked in the area this year, of which five were hijacked, he said. Pirates are still holding seven vessels and 118 crew members for ransom.