(Photo: REUTERS/Turkish Chief of Staff/Handout)

KUALA LUMPUR, Malaysia (AP) — Sea piracy worldwide surged to 266 attacks in the first half this year, up 36 percent from a year ago, as Somali pirates became bolder and raided more vessels, a global maritime watchdog said Thursday.

Sixty-one percent, or 163 of the attacks globally, were carried out by Somali pirates largely in the Arabian Sea frequented by crude oil tankers, the International Maritime Bureau's piracy reporting center in Kuala Lumpur said in a statement. This was up from 100 attacks by Somali pirates in the same period last year.

"In the last six months, Somali pirates attacked more vessels than ever before and they're taking higher risks," said the maritime bureau's director Pottengal Mukundan.

For the first time, pirates in June fired on ships in rough seas in the Indian Ocean during the monsoon season, he said. In the past, they stayed away from attacking in difficult conditions.

However, the bureau said Somali pirates hijacked only 21 ships, down from 27 in the first half last year, thanks to increased ship vigilance and international navies' action in disrupting pirate groups off East Africa.

"It is vital that this naval presence be sustained or increased," it said.

As of the end of June, Somali pirates were holding 20 vessels and 420 crew members, and demanding ransoms of millions of dollars for their release, the bureau said.

They fired at 76 vessels, killing seven people and injuring 39. At the same time, 62 piracy attempts were reported to have been thwarted in the first half of the year.

Also this year, a wave of violent and highly organized attacks has hit the coast of West Africa.

Twelve tankers were attacked off Benin since March in an area that was free of pirates last year, the bureau said. Five of the vessels were hijacked and forced to sail to unknown locations where pirates ransacked and stole the ship equipment and oil cargo, it said.

In neighboring Nigeria, the bureau said it was informed of six incidents but it was aware there were at least 11 other attacks not reported by ships.

Elsewhere, 50 incidents were recorded for Indonesia, Malaysia, Singapore Straits and the South China Seas in the first six months, with three tugs hijacked by armed pirates.