KUALA LUMPUR, Sept. 23 (AFP) - A global maritime watchdog called Tuesday for more anti-piracy operations in the South China Sea due to a marked increase in attacks in the southern fringes of the ocean.

Noel Choong, head of the International Maritime Board's piracy reporting center, told AFP there were 19 attacks reported in the area for the first nine months of this year compared to 17 for the whole of 2008.

''We are urging countries in the area to increase anti-piracy operations as this helps to reduce such attacks,'' he said.

The affected area lies in a triangle between Indonesia's Anambas Islands, Tioman Island off Malaysia and the eastern Singapore Straits.

Choong said crews needed to be more vigilant when sailing through the area.

Pirates attacked a Singapore-flagged liquefied petroleum gas tanker heading through the Singapore
Straits on Saturday. Six pirates boarded the tanker and attacked the crew using machetes before robbing them and fleeing.

''These vessels should mount anti-piracy watches in the triangle because once these pirates are spotted, they do not attack unlike in Somalia where the pirates attack regardless of being identified,'' he added.

Choong said most of the pirates in the triangle were armed with guns and knives and that the maritime board had sent out an alert to vessels in May this year warning them of the dangers in the area.

''Every time we inform the authorities the attacks go down but they then slowly creep up, so we are keeping a very close eye on the region,'' Choong said.

Pirate attacks have more than doubled globally in the first half of 2009 because of rampant high-seas raids by Somali pirates, according to the International Maritime Board.

It earlier said incidents of piracy rose to 240 from 114 worldwide in the six months to June, compared with the same period a year ago.