Somali pirates hijacked a vessel carrying 22 crew members that was heading to Durban, South Africa, early Wednesday morning. It was the fourth attack on a ship off the Somali coast in three days.

A news release from the European Union Naval Force on Somalia said the vessel, MV Filitsa, was attacked in the south Somali Basin of the Indian Ocean, 400 nautical miles north-east of the Seychelles.

It was now heading north, the force said. The ship was crewed by three Greek and 19 Filipino sailors.

Yesterday pirates attacked MV Nele Maersk, a Danish-flagged container ship. The attack took place not far from where the crude oil tanker, BW Lion, was attacked on Monday. Neither of the attacks succeeded.

Also yesterday, another attack took place in the southern part of the Somali Basin. Automatic weapons were fired on the MV Felicitas Rickmers, a container ship.

By employing evasive manoeuvres and other anti-piracy measures, the ship also managed to evade the attack. Pirates opened fire but no casualties were reported and the ship managed to outrun the pirates.

On October 27 European Union naval forces seized seven suspected Somali pirates after an attack on a French fishing vessel east of Mogadishu.

The North Atlantic Treaty Organization (NATO) Shipping Centre recommended in a warning posted on its website Wednesday that "all vessels not making scheduled calls to ports in Somalia, Kenya or Tanzania keep as far from the Somali coast as possible."

The centre advised shipping heading south or north to maintain a course at least 600 nautical miles east of the African coastline, sailing east of the Seychelles, and to avoid the area between the Somali coast and north and west of the Seychelles.

"While navigating in the region," NATO said, "vessels are urged to operate at a heightened state of readiness, maintaining strict 24-hour anti-piracy visual and radar watches, actively implement recommended anti-piracy measures and regularly report their position/course/speed..."