GENEVA - The United Nations warned Wednesday that piracy off Somalia's coast could deprive the country's poorest of much-needed food aid.

The World Food Program has managed to deliver a steady flow of relief over the last 18 months, thanks largely to its use of naval escorts for supply boats approaching the Somali capital of Mogadishu, the northeast port of Berbera and Bosaso in Somalia's Puntland.

But before those shipments are turned over to the U.N. aid agency, they are often unescorted and vulnerable to attack.

The recent surge in attacks in the Indian Ocean _ including two in a week on U.S. aid ships _ has raised questions about whether more escorts are needed.

Both American ships were unescorted as they headed for Mombasa, Kenya, to hand their supplies over to WFP. The Liberty Sun took some damage during its attack Wednesday, but managed to escape and reach the Kenyan port with its crew unharmed.

The incident followed the liberation Monday of the captain of another U.S. ship carrying food aid, the Maersk Alabama, who had offered himself as a hostage to save his 19-man crew from the pirates. The Maersk Alabama had been bringing food aid as a donation for WFP, and was not contracted by the agency.

"The ship escort system has worked quite well," said Emilia Casella of WFP, which has been using naval escorts since November 2007. "When we've had escorts, we have had not any incidents of piracy on WFP-contracted ships."

WFP shipped 260,000 tons of food to millions of Somalis suffering from drought and violence last year, Casella said.

But the agency is worried about a cargo ship hijacked Tuesday while heading to Mumbai, India, to pick up 7,327 tons of WFP food for Somalia. The Lebanese-owned MV Sea Horse was not under WFP contract, but would have flown under the agency's flag once the food was loaded, Casella said.

"We're very concerned that people in Somalia would go hungry unless the Sea Horse is released," she said.

WFP is feeding 3.5 million Somalis this year, or about half of the country's inhabitants. This requires shipping 43,000 tons of food every month _ some 90 percent of which is sent by sea, Casella said. Flying in food aid is too expensive, and roads in the lawless country are plagued by bandits.

However, providing naval escorts for all boats and merchant ships in the vast Indian Ocean area would be hugely expensive.

Somali pirates have become bold in launching attacks from speedboats far from their homeland, and the seajackings have brought in millions of dollars in ransom. This year, Somali pirates have attacked 79 ships and hijacked 19.

Six ships with WFP food were hijacked over three years before 2007, when France, Denmark and the Netherlands stepped in to offer naval assistance. The system was interrupted in June, when a Dutch warship left the area, leading to a six-week suspension of WFP food shipments to Somalia. Canada took over escorting the food aid in August, followed by the European Union.

Some aid organizations have been less affected by the surge in piracy, due to logistical differences.

The International Committee of the Red Cross has major aid operations in Somalia, but buys food and other items from local traders, who arrange the shipments themselves, spokesman Marcal Izard said. Other shipments, such as medical gear and equipment for water installation, are brought into the country by air, he said.

But the number of agencies willing to work in Somalia has been curbed by other plagues, such as abductions and killings.

CARE International pulled out of central and south Somalia in October after receiving public threats by some local militia groups. The militia accused CARE and another aid agency, the International Medical Corps, of committing "crimes against Islam and the jihad" and warned them to leave areas controlled by Islamic forces.

The country has been without an effective government since 1991, when warlords overthrew a dictatorship and then turned on one another.

A service of the Associated Press(AP)