Global shipping officials warned Wednesday that pirate attacks off Somalia's coast have spiraled to terrifying levels, with U.S. and international navies failing to protect seafarers from being kidnapped.

Somali pirates have abducted more than 100 crew members of various nationalities, often seizing them in international waters and spiriting them away to Somalian territory, said Capt. Pottengal Mukundan, director of the British-based International Maritime Bureau, a shipping security watchdog.

The attacks have increased despite the permanent presence of an international task force in the northern Indian Ocean that patrols the Somali coast in hopes of intercepting terrorists. U.S. destroyers are normally assigned to the task force and patrol in pairs.

"The figures are frightening and unacceptable because the pirates operate with impunity," Mukundan said at a maritime security conference. "If the navies fail to intervene, we fear the situation will get a lot worse before it ever gets better."

Somalia lies close to crucial shipping routes connecting the Red Sea with the Indian Ocean, where valuable cargo and carriers pass. Officials say Somalia's 1,880-mile coastline makes it difficult to prevent pirate attacks.

Somali pirates are trained fighters, often dressed in military fatigues, and using speedboats equipped with satellite phones and Global Positioning System technology. They target passenger and cargo vessels for ransom or loot, and use the money to buy weapons.

Naval authorities, who also include Dutch and Belgian forces, can boost security by checking suspicious vessels to ensure they are not being commandeered by bandits who are typically armed with automatic weapons, anti-tank rocket launchers and grenades, Mukundan said.

Somalia has had no effective government since 1991, when warlords ousted a dictatorship then turned on each other.

Thomas Timlen, a security expert of Denmark-based BIMCO, the largest international shipping association, said stronger patrols have been effective in curbing piracy in other territories, such as the Malacca Strait shared by Malaysia, Indonesia and Singapore.

"Tighter security will work if it is implemented off Somalia," Timlen said.

Sailors captured by Somali pirates this year have included Chinese, Danish, Indian, South Korean and Vietnamese citizens.