The German navy foiled a pirate attack on a container ship in the Gulf of Aden off Somalia on Tuesday and arrested nine pirates, the military in Berlin said.

In this image relased by the US Navy, suspected pirates keep their hands in the air as directed by a patrol from the guided-missile cruiser USS Vella Gulf in the Gulf of Aden, in February 2009. The German navy foiled a pirate attack on a container ship in the Gulf of Aden off Somalia on Tuesday and arrested nine pirates, the military in Berlin said. [Chinadaily.com.cn/agencies]

The frigate Rheinland-Pfalz received a distress call early Tuesday from the German-owned ship saying she was under fire from pirates armed with bazookas and machine guns, a statement said.

The frigate dispatched a helicopter which together with another chopper from the US naval ship Monterey stopped the attempted attack by firing warning shots.

The US helicopter then returned to its ship and the Rheinland-Pfalz steamed the 50 nautical miles to the area, boarded the pirates' vessel and took the nine into custody, the German military said.

"They are currently being questioned about who they are and their activities," it said.

The military said it had 48 hours to interrogate the pirates.

The container ship in question was the MV Courier, sailing under the flag of Antigua and Barbuda. According to the shipping firm running her, the pirates fired bazookas at the vessels but missed their target.

No one was injured, Jens Winter, a director at the company told AFP.

More than 100 ships were attacked last year by pirates in the Gulf of Aden which is now patrolled by naval warships from the United States, EU and other countries including China to protect vessels in the vital waterway.

In November, pirates captured the world's attention when they hijacked the Saudi-owned super-tanker Sirius Star, carrying two million barrels of crude oil, and demanded a 25-million-dollar ransom for the ship and its crew.

The pirates, heavily armed and using high-powered speedboats, prey on a key maritime route leading to the Suez Canal, through which an estimated 30 percent of the world's oil transits.

German navy from frigate Rheinland-Pfalz detain pirates in the Gulf of Aden off Somalia's coast on March 3, 2009, in this picture made available on March 4, 2009. [Chinadaily.com.cn/agencies]

They are believed to number around 1,200 former and seasonal fishermen and coast guards, many of them from lawless Somalia, which has been ravaged by years of conflict and starvation.

Nevertheless, the number of pirate attacks has been sharply reduced this year following the sending of more ships to the area, including from the European Union's anti-piracy operation Atalanta in mid-December.

Earlier Tuesday, the US military said it had released nine suspected Somalian pirates after it did not find enough evidence to prosecute them.

The nine were arrested on February 12 after an Indian-flagged vessel reporting that it been fired upon at night by a small skiff and that pirates were attempting to board.