OSLO - Somali pirates on Friday released the Norwegian tanker Bow-Asir and its crew, having held it since March 26, its owners said in a statement Friday.

"The chemical tanker Bow Asir was released on Friday 10th April 2009. However, the ship is still sailing in dangerous waters," Norway's Salhus Shipping said in the statement.

"All crew are unharmed and we wish to thank them for their handling of this difficult situation," the company said.

The Bahamas-registered vessel was carrying 20,000 tonnes of chemical products and had a 27-member crew when it was attacked by up to 18 pirates about 250 nautical miles off the southern Somali port of Kiasmaayo.

The crew was made up of 19 Filipinos, five Poles, one Russian and Lithuanian and a Norwegian skipper.

Since April 4, Somali pirates have stepped up their attacks. They have hijacked a US container ship, a small French sailing yacht, a British-owned Italian-operated cargo, a German container carrier, a Taiwanese fishing vessel and a Yemeni tugboat.

Some of the pirates' most spectacular successes came late last year when they seized a Ukrainian cargo loaded with combat tanks and other weaponry, as well as a Saudi super-tanker carrying 100 million dollars in crude oil.

The combined ransoms paid for the release of these two ships alone is believed to be around eight million dollars (six million euros) and the pirates are known to significantly reinvest in better equipment.