Manama, Bahrain  - Suspected Somali pirates have attacked a US Navy support boat off the coast of the troubled Horn of Africa state, the US Navy said Thursday.

The two supply vessels were chased for more than an hour by two pirate boats, taking emergency evasive action after being fired upon by small arms in the attack on Wednesday morning, the US Navy 5th Fleet said in a statement.

So far in 2009 there have been 97 attempted attacks on merchant vessels, 27 of which have been successful, in what is now the most notorious area for piracy in the world.

The supply boats were "approached by suspected pirates off the eastern coast of Somalia and took evasive action to prevent a successful attack," the statement said.

The two pirate boats got within two miles of the supply boats, firing small arms munitions, but which fell short of reachign the target.

Eventually the two attacking boats gave up and retreated.

An increasing number of merchant vessels are now being trained to take evasive maneuvers from pirate attacks, and other defensive measures, such as on-board security teams, to protect their ships and their cargoes.

More than 30,000 vessels transit the Gulf of Aden annually. (dpa)