A Somali pirate spokesman says his group will not release a hijacked Ukrainian cargo ship loaded with arms for less than $20 million.

Sugule Ali told the Associated Press on Thursday the pirates would "never" reduce the ransom of the Ukrainian freighter loaded with 33 Soviet-designed tanks and other weapons. The MV Faina was seized last Thursday and is now anchored off the coast of central Somalia.

The pirates have been negotiating with the ship's owners. There are 20 crew aboard the ship.

Ali warned that any attempt at deception or commando raids on the ship would be met with repercussions.

Pirates off Somalia's lawless coast have raked in up to $30 million in ransoms this year alone, a London-based think tank reported.

A flotilla of U.S. navy warships have surrounded the MV Faina, which is anchored off the central Somali coast, to ensure that the pirates don't unload any of the weapons. The cargo ship and its 21-man crew were hijacked Sept. 25, and the ship's ammunition and heavy weapons have sparked fears among Western governments that the arms could end up in the hands of terrorists.

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Somali officials on Wednesday authorized foreign powers to use whatever force is necessary to free the ship.

The report Thursday by Roger Middleton for Chatham House said the millions being earned by pirates in ransom were already being used to pay for the war between the shaky Somali government and Islamic insurgents, some of whom are on a U.S. State Department list of terrorists.

"The international community must be aware of the danger that Somali pirates could become agents of international terrorist networks," Middleton warned, but admitted there was no explicit evidence yet showing that ransoms had bought weapons outside Somalia.

Piracy in 2008 has more than doubled from the previous year, with over 60 attempted attacks or successful hijacks reported. Most pirate attacks occur in the Gulf of Aden, one of the world's busiest shipping lanes, north of Somalia. But recently pirates have been targeting Indian Ocean waters off eastern Somalia.

In a separate report Thursday, a Danish intelligence company specializing in maritime security said there has been a dramatic increase in the number of seamen held by Somali pirates in September.

Risk Intelligence said pirates held 374 people captive after raids off the Horn of Africa last month. That compares with 292 hostages in all of 2007.

Company manager Hans Tino Hansen says the Somali pirates make an average of $1 million per hijacked vessel and hold freighters for an average of five weeks before freeing them.

The Navy says two other pirated cargo ships are anchored in the same area as the Faina.

On Wednesday, at least eight European Union countries offered to form a new force to help protect shipping off Somalia — a move that eventually could give the U.S. Navy crucial support in the area.

The Bahrain-based spokesman of the U.S. 5th Fleet, Lt. Nathan Christensen, hailed the EU move as "a step in the right direction." He said the Navy got reports of three failed attacks Thursday in the Gulf of Aden.

The final destination of the Faina's weapons is in dispute. Kenyan officials claim the weapons are for domestic use, but American defense officials, Western diplomats and a Kenyan maritime official have said the weapons were intended for southern Sudan.

The Kenyan maritime official, Andrew Mwangura, was arrested late Wednesday and charged with making inflammatory statements. He was the first official to say the weapons were intended for Sudan.

Kenya has been embarrassed by claims the arms were headed to Sudan because it helped broker an end to Sudan's north-south war in 2005.

In Ukraine, Prime Minister Yulia Tymoshenko — who is locked in a political battle with the president — called for an investigation into the true destination of the weapons.

Despite the Somali government's authorization to use force against the pirates, U.S. Defense Department spokesman Bryan Whitman declined to comment on any possible military operations

In the past, the U.S. military has launched air strikes in Somalia and is known to have secretly sent special forces into Somalia to go after militants linked to Al Qaeda.