An Italian vessel carrying 23 crew members was hijacked by five pirates about 620 miles east of the Somali coast on Monday, the D'Alesio shipping company said.

"There has been no contact with the ship since 6:44 (0444 GMT) this morning," when the captain sent a message saying the vessel was under attack and he had activated "the security operating procedure," the company said.

"After 10 hours without news, we can consider the ship hijacked," a spokesman from the Livorno-based company told AFP.

There are seven Italians, ten Ukrainians and six Indian nationals aboard.

Commander Harrie Harrison, spokesman of the EU counter-piracy mission, told AFP that warships and aircraft will search for the missing ship.

"We will investigate as soon as we are able to get an asset in the area to see if we can locate the ship," he said.

The owners of the M/V Montecristo said it was "actively collaborating with all the related Italian and international authorities to respond to the emergency."

Italy's foreign ministry said it was closely monitoring the situation.