NAIROBI (Reuters) -- U.S. Navy vessels are staying close to a Ukrainian ship hijacked by pirates with 33 tanks and other military hardware on board in one of the most worrying of a rash of attacks this year off lawless Somalia.
The Persian Gulf-based Fifth Fleet sent the destroyer "USS Howard" and other boats to within sight of the "MV Faina" and its 21 crew members taken last week en route to Kenya's Mombasa port.
"There are now several Fifth Fleet ships in the vicinity," said the fleet's deputy spokesman, Lieutenant Nathan Christensen.
"We are deeply concerned about the state of the crew and the cargo of the ship. Our goal is to maintain a vigilant and visual watch over the ship while negotiations take place."
The pirates are demanding $20 million ransom for the ship, which has grenade launchers and ammunition as well as the T-72 tanks, according to regional maritime sources.
"The Americans are there, but they cannot attack because the cargo is too dangerous," said Andrew Mwangura, whose East African Seafarers' Assistance Program is monitoring the saga.
The seizure off Somalia, which is engulfed in civil war, has dangerous ramifications for the turbulent East African region and the commercially strategic shipping lanes off Somalia.
The Gulf of Aden between Yemen and north Somalia is a major global sea artery used by about 20,000 vessels a year heading to and from the Suez Canal. The Indian Ocean waters off south Somalia are also busy, including with UN aid shipments.
Somali pirates have taken about 30 ships this year.
Analysts say that while the pirates would probably be unable to offload the "Faina's" tanks, the other equipment on board or a large ransom could give a dangerous tilt to the war in Somalia where Islamists rebels are battling the government.
Controversy Over Destination
Islamist leader Sheikh Hassan Dahir Aweys told Reuters the rebels were not involved. "Piracy is not our hobby and we are sorry for being linked to everything that is bad," he told Reuters from Eritrea, where he is based.
Aweys noted that during the Islamists' six-month rule of south Somalia in 2006, they effectively halted piracy. "But no one congratulated us," he said.
Should the arms on the Ukrainian ship find their way into Somalia, however, that would be "nothing peculiar" given that Ethiopian backers of the Somali government and Ugandan peacekeepers were bringing weapons in, Aweys added.
Kenya says the Ukrainian ship's cargo was intended for its military. But some analysts believe the equipment may have been headed for south Sudan in possible breach of an arms embargo.
"There have been alarming propaganda by the pirates to media that the weapons are not for the Kenyan military. This is a tactic by the terrorists to try and fend off reprisals against them," Kenyan government spokesman Alfred Mutua said.
The "Faina" was anchored on September 29 a few kilometers off the Somali coast near the town of Hobyo.
"We are not going to let them offload the cargo," said Fifth Fleet deputy spokesman Christensen, declining to say whether the U.S. ships would engage if the pirates tried.
Mwangura said a helicopter, probably U.S., had been buzzing the "Faina." He said one of crew member, a Russian, had died on board due to sickness since the hijack.