The U.S. Navy said one of its cargo ships has evaded a pirate attack off the eastern coast of Somalia.
A statement from the Navy's 5th Fleet said two pirate skiffs pursued the USNS Lewis and Clark for more than an hour on Wednesday.
It said the pirates closed to within one nautical mile before lookouts spotted them, and the Lewis and Clark increased speed.
The Navy said small arms fire from the pirates fell well short of the ship's stern.
The Lewis and Clark recently served as a temporary detention facility for Somali pirates captured at sea.
Earlier Thursday, Somali pirates hijacked a Dutch ship, the MV Marathon, with up to 18 crew members. The ship was seized in the Gulf of Aden carrying a cargo of coal.
On Tuesday, Somali pirates captured a German-owned cargo ship in the gulf, 120 kilometers south of Yemen.
Somali pirates are now holding around 20 ships with more than 250 hostages.
About a dozen nations are conducting naval patrols off the coast of Somalia to protect commercial vessels. But officials have said the only real solution is to stabilize the situation on the mainland.
Somalia's weak central government is fighting an Islamist insurgency and is unable to stop the piracy.
The piracy is fueled by ransom payments, some in the millions of dollars, that many owners have paid.
Some information for this report was provided by AP and Reuters.