The number of attacks on ships in the South China Sea is at a five-year high, according to officials.

The increase of naval patrols in the Straits of Malacca have forced pirates in Asia to move their operations to the South China Sea, the officials said, as reported by Associated Press.

At least ten ships have been attacked in the South China Sea so far this year, the latest on Saturday when six pirates boarded a Singapore-registered liquefied petroleum gas tanker.

According to the regional cooperation agreement on combating piracy and armed robbery against ships in Asia, or ReCAAP a total of 38 ships were attacked in Asia in the first six months of 2009, of which eight were hijacked and the rest robbed at sea.

Of the eight hijackings, seven were in South China Sea.

Worldwide, pirate attacks more than doubled in the first half of 2009 amid a surge of raids on vessels in the Gulf of Aden and the east coast of Somalia, according to the International Maritime Bureau’s piracy reporting centre in Kuala Lumpur, writes Associated Press.