Italy says U.S. and British forces have freed an Italian vessel that was hijacked off Somalia on Monday.

The MV Montecristo had been seized 1,000 kilometers off Somalia's eastern coast, carrying 23 crew members from Italy, Ukraine and India.

The Italian Foreign Ministry said Tuesday that the ship was freed by units of the U.S. and British navies, operating under NATO's anti-piracy initiative Operation Shield.

Details on the operation were sketchy, but the ministry says the 11 pirates who hijacked the ship surrendered and were taken into custody.

Meanwhile, the Italian shipowners association says military forces will soon be stationed on all Italian merchant ships to protect against attacks by Somali pirates.

The trade association Confitarma made the announcement Tuesday, one day after pirates hijacked the Montecristo.  An agreement with Italian Defense Minister Ignazio La Russa is expected to be signed later in the day.

Some ships already carry security guards on board, but they are not always armed.  The higher security has not dissuaded Somali pirates who have hijacked scores of ships and collected hundreds of millions of dollars in ransoms over the past few years.