A hijack drama is playing out off the coast of Somalia, where pirates have seized a cargo ship reportedly carrying Russian T-72 tanks destined for Kenya.

A United States Navy report issued on Sunday said the USS Howard, a destroyer from the U.S. 5th Fleet, was patrolling within sight of the Motor Vessel Faina, a Belize-flagged cargo ship which was captured by pirates on September 25.

The Howard's commanding officer, Commander Curtis Goodnight, said: "My crew is actively monitoring the situation, keeping constant watch on the vessel and the waters in the immediate vicinity."

Agence France-Presse reports that the pirates, despite being surrounded by the Howard and two other foreign warships, have demanded a ransom of U.S. $20 million.

Speaking by satellite phone to AFP, Sugule Ali said the pirates were not afraid of the warships: "That will not make us to abandon the ship or to refrain from asking (for) the money. There is no shortage of food supply and all the crew members are healthy and well including ours."

The Faina is anchored near the Somali harbour city of Hobyo.

In Nairobi, The Nation newspaper reported Sunday that the Ukrainian-operated ship was carrying 33 battle tanks and "huge quantities of ammunition and grenade launchers" for the Kenyan armed forces.

It reported that the Kenyan Navy was headed for the Faina, where it would take part in a joint operation, including a Russian warship, to recover the hijacked ship.