A container ship repelled an attack by suspected pirates off the coast of Somalia with the aid of sonic weapons, it was revealed today.

A security team deployed Long-Range Acoustic Devices (LRADs) and small arms fire to repel a skiff approaching the Maersk-Alabama this morning.

Four suspected pirates came within 275 m of the ship before they broke off their approach.

The LRAD is a crowd-control and hailing device developed by American Technology Corporation.

It can emit a tone at a level as high as 146 dB at ranges of up to 300 m and can permanently damage hearing.

Commenting on the incident, vice admiral Bill Gortney, commander of US Naval Forces Central Command, said: “Due to Maersk-Alabama following maritime industry’s best-practices such as embarking security teams, the ship was able to prevent being successfully attacked by pirates.

“This is a great example of how merchant mariners can take pro-active action to prevent being attacked and why we recommend that ships follow industry best practices if they’re in high-risk areas.”

The ship was briefly seized by pirates in April and the ship’s captain, Richard Phillips, was held hostage for five days.

He was freed in an operation mounted by US naval forces, who killed three pirates and took another into custody.