Andrew Mwangura, East Africa's Coordinator of the Seafarers Assistance Program (SAP), said the pirates released the Maltese-flagged Greek ship MV Centauri on Thursday.

"The ship was freed yesterday (Thursday) along with the 26 crew members. It is now underway to Mombasa and I don't know whether ransom was paid to secure its release," Mwangura told Xinhua by telephone from Mombasa.

The ship had a crew of 26 Filipinos and was about to discharge 17,000 tons of bulk salt at the Mombasa port when it was seized off the coast of Somalia in September.

It is currently sailing to the Kenyan port of Mombasa.

The release of the MV Centauri came two days after the pirates release MV Genius, also a Greek ship, and all its 19 crew.

Somali pirates seized the tanker, MV Genius, on September 26 in the Gulf of Aden near the Horn of Africa, waters that are highly dangerous for shipping because of the rampant piracy.

The developments came as pirates hijacked a chemical tanker on Friday.

Mwangura said the Biscaglia, flying under a Liberian flag, was seized with 25 Indians, two Bangladeshis and three Britons on board.

"Ship managers are Ishima Pte Limited of Singapore. Owners are Winged Foot Shipping Limited, Marshall islands," Mwangura said.

The incident is the latest in a series of increasingly brazen attacks by pirates off Somalia. It is not yet known if a ransom has been demanded.

Warships from Denmark, India, Malaysia, Russia, the United States and NATO patrol the vast international maritime corridor off Somalia, escorting some merchant ships and responding to distress calls.

In the past two weeks, Somali pirates have seized nine vessels, including a huge Saudi tanker carrying 100 million U.S. dollars worth of crude oil.

This high profile case has outraged the maritime industry and the international community has called for joint action against piracy.

This year there have been more than 90 attempts at capturing ships by pirates in the Gulf of Aden, 39 of which have been successful, according to maritime organizations.