Armed pirates in speedboats hijacked a Greek chemical tanker with 20 crew members in the Gulf of Aden near Somalia, a maritime official said Saturday.

The Greek ship, which was flying a Panamanian flag, was traveling from Southeast Asia to Europe when it was seized Friday, said Noel Choong, head of the International Maritime Bureau's piracy reporting center in Kuala Lumpur.

No further details were immediately available, he said.

The attack comes despite increased international cooperation to crack down on pirates in the Gulf of Aden.

Friday's hijacking pushed the number of attacks this year in the African waters to 69. A total of 27 ships have been hijacked, and 11 remain in the hands of pirates along with more than 200 crew members, Choong said.

He said more serious action needs to be taken to intercept pirate boats and detain the bandits.

"As long as there are no firm deterrents, pirates will continue to attack," Choong said.

Momentum has been growing for coordinated international action following the Sept. 25 hijacking of the Ukrainian ship MV Faina, which was carrying tanks and other heavy weaponry.

The U.N. Security Council this past week called on countries to send naval ships and military aircraft, and U.S. warships are being diverted from counterterrorism duties to respond to the sea bandits.

NATO ministers agreed Thursday to send seven ships within two weeks to the area, where six U.S. warships are already surrounding the Faina. Russia also announced it would cooperate with the West in the fight, and several European countries have said they would launch an anti-piracy patrol.

Somalia, which has not had a functioning government since 1991, has been impoverished by decades of conflict, and piracy by Somali gangs has emerged as a lucrative racket that brings in millions of dollars in ransoms.