Pirates have hijacked a Turkish cargo ship and a Malaysian tug boat and attacked three other vessels in the Gulf of Aden in the past week, a global maritime watchdog said on Wednesday.
The latest incidents came as a European Union naval task force took over from a NATO operation patrolling the pirate-infested seas near the Horn of Africa with six warships and three surveillance planes.
In the first hijacking, pirates armed with rocket-propelled grenades and automatic weapons boarded a Malaysian tug on Tuesday, Noel Choong, head of the International Maritime Bureau piracy reporting centre in Kuala Lumpur told AFP.
The tug with 11 crew on board was heading to Malaysia from the Middle East.
Choong said a Turkish cargo ship was hijacked, also in the Gulf of Aden on Tuesday, by a gang of pirates who fired automatic weapons from two speed boats.
"They were armed with RPGs. They opened fire at the ship and then boarded it. The ship was heading to Europe from the Middle East," he said.
Choong said the EU armada, which officially started operations on December 8 and whose flagship was to begin its mission on Wednesday, had so far been unable to stop the attacks because the waters off Somalia were so wide.
"Despite the European Union armada to patrol the Gulf of Aden, the pirates manage to attack and hijack ships because the number of warships is insufficient to secure the vast sea," he said.
Choong said in three other incidents last week, Somali pirates attempted to hijack a Singapore tanker, an Italian cargo ship and a Greek ship.
"Coalition forces deployed a helicopter to ward off the attacks. The three ships managed to escape," he said.
Choong also said that the Indian navy last on Saturday captured a suspected pirate's "mother ship" and detained 24 pirates -- 12 Yemeni and 12 Somali -- and seized weapons including RPGs and AK47 automatic rifles.
Indian officials earlier said 23 pirates were captured.
"The pirates are being held by the Indian navy," he said.
Choong said 108 ships have been attacked by pirates off Somalia so far this year and 42 ships hijacked.
Fourteen foreign merchant vessels and their crew of 240 are currently being held by gunmen in the area where the northeast tip of the Somali coast juts into the Indian Ocean.
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 per cent of the world's oil transits.
The pirates 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.