A US ship carrying humanitarian aid was attacked Tuesday by Somali pirates. Damage was caused but the crew were not injured, the owner of the ship said in a statement.

The Liberty Sun, with its crew of about 20 Americans, was on its way to Mombasa, Kenya, when the pirates fired rocket-propelled grenades and automatic weapons at it, the ship's owner Liberty Maritime Corp. said.

The cargo ship carried food for famine-stricken nations in Africa.

US Navy sailed to aid when the vessel reported being attacked but the pirates had left when the destroyer Bainbrighe arrived some six hours later, US Central Command spokesman Jack Hanzlik said.

The vessel continued on its way to Kenya under Navy escort although a rocket penetrated the bulkhead and caused a small hole, the company said.

President Barack Obama vowed Monday to "halt the rise of piracy," as the Somali pirates continue attacking and hijacking ships on the open sea. They seized a total of four ships with 60 hostages Tuesday.

(Xinhua News Agency April 15, 2009)