The pirates carried out 37 successful hijackings of ships in the first 10 months of this year while up from 33 in the same period of 2009, the report indicated. UN Secretary General Ban Ki-moon called the pirates a "scourge".

International Maritime Organization (IMO) inquiries "imply that the level of violence employed by the pirates has increased," said the UN document prepared for the UN Security Council.

The number of attacks has fall from 193 to 164 as the western naval patrols are patrolling the sea, the UN said, quoting IMO figures. But the pirates had seized 389 people and 18 vessels for ransom in October 11.

But as of October 11, 389 people and 18 vessels were being held ransom by the pirates. They have also increased their scope of action in the Indian Ocean by setting up bigger attack fleets.

"The plight of the 389 hostages currently held by pirates on Somali territory is of particular concern," Ban Ki-Moon commented in a report released by the UN.

The hostages are including crew from Africa, Asia and Europe, and also tourists from Western Europe.

A British couple, Paul and Rachel Chandler, whose yacht was captured near the Seychelles in 2009, recently marked a year in captivity, with negotiations for their release at a standstill.

"In many cases, the victims' whereabouts are not known, and no independent entity is able to verify their state of health and well-being," Ban said.

The UN chief insisted that Somalia's civil war must be dealt with to beat piracy. "The severity of the problem off the coast of Somalia is a relatively recent phenomenon," Ban said in the report.

"Yet I am afraid that the problem will not only be with us for a long time to come, but also has the potential to become worse unless both Somalis and the international community address its root causes."

Some of the pirates attack now happen up to 1,300 nautical miles off the coast and targeted "ever-larger freighters".

The report said that the foreign naval force in the Gulf of Aden had reduced the number of attacks and hijackings in the zone but the pirates now roam the southern end of the Red Sea and even venture as far as the Maldives.

Only NATO ships had interrupted 148 pirate attacks this year, according to the report.

"This eastward and southward shift in piracy has brought a much greater maritime area under threat," said the report.

The report said there was evidence the pirates have moved into new criminal areas such as smuggling contraband and trafficking people.