Pirates hijacked a Turkish ship with 20 crew off the coast of Somalia but at least six other ships have fended off pirate attacks in the last two days, officials said Thursday.

The M/V Yasa Neslihan freighter was boarded by pirates in the Gulf of Aden on Wednesday, the International Maritime Bureau in Malaysia said.

Noel Choong, a Maritime official, said an Italian-operated cargo ship with 26 crew managed to escape a pirate attack in the same area Tuesday with unspecified aggressive maneuvers.

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NATO sent three ships over the weekend into the Gulf of Aden — one of the world's busiest shipping lanes — for anti-piracy patrols and to escort cargo vessels. But attacks have continued unabated.

On Wednesday, the U.S. Navy said commercial shipping vessels foiled five recent attempted hijackings by pirates in the Gulf of Aden. In one instance, a Spanish military patrol plane thwarted pirates trying to hijack an oil tanker by buzzing them three times and dropping smoke canisters.

At least 77 ships have been attacked in the African waters this year. Thirty-one ships have been hijacked, and 10 remain in the hands of pirates along with nearly 200 crew members.

"Pirate attacks are still continuing in the region, despite additional security measures. It is worrying," Choong told The Associated Press.

Turkey's state-run Anatolia news agency, quoting unnamed Turkish maritime officials, said Turkey had asked NATO forces to help end the hijacking off Somalia.

The Yasa Neslihan was carrying iron ore from Canada to China. Fehmi Ulgener, a spokesman for Yasa Holding, which owns the vessel, said the company learned the ship had been seized through the vessels' alarm system.

He told the Associated Press that Turkish authorities were in contact with "various authorities" to find a way to rescue the ship but have had no contact with the pirates.

Several U.S. Navy's 5th Fleet warships also have also been deployed off the Horn of Africa surrounding the MV Faina, a Ukrainian ship loaded with tanks and heavy weapons that was seized by Somali pirates on Sept. 25.

Each year about 20,000 vessels pass through the Gulf of Aden, which links the Indian Ocean with the Suez Canal and the Mediterranean Sea.

Somalia is caught up in an Islamic insurgency and has no functioning government, no navy and no coast guard to police its coast.

This week the European Union announced at least four warships backed by aircraft would begin policing the dangerous waters in December. The EU flotilla will eventually take over patrolling the area from NATO ships.