The U.S. Navy has fired warning shots across the bow of a Dutch ship that has been boarded by armed pirates off the coast of Somalia, FOX News has learned.

The USS Carter Hall also fired on three small boats that surrounded the commercial ship, the "Danica White," after her crew messaged for assistance after being boarded by pirates, the Navy said.

The incident began Saturday and as of Monday the Danish ship's crew was still believed to be held at gunpoint by an unknown number of pirates who forced the vessel into Somalia's territorial waters. There have been no reports of casualties.

The USS Carter Hall remains nearby in international waters, monitoring the situation. The Danish ship, which the Associated Press reported was owned by H. Folmer & Co. of Copenhagen, has not requested further assistance.

On Saturday, Jorgen Folmer, a spokesman for the Danish shipping company, said a French naval vessel in the area had confirmed the ship and its crew of five was hijacked but was unable to intervene because it could not enter Somali waters.

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A maritime official said Monday that Somali pirates who have been holding a Taiwan-flagged fishing vessel since mid-May killed one of the 16 crew members because the ship's owners have not paid a ransom.

The pirates threatened to kill other crew members if their demands are not met, said Andrew Mwangura, head of the Kenyan chapter of the Seafarers Assistance Program.

He cited a relative of one of the captives, who was allowed to call his family.

"The gunmen have established contact with the owner of the ship but it appears that he was giving them empty promises," Mwangura said.

The ship — Ching Fong Hwa 168 — had two Taiwanese and 12 Chinese crew members on board when it was hijacked 137 miles northeast of the Somali capital, Mogadishu. Mwangura did not know the nationality of the victim.

Somalia does not have a coast guard or navy after more than a decade of anarchy. The current government was formed in 2004 but has struggled to assert any real control throughout the country.

Somali pirates are trained fighters, often dressed in military fatigues, using speedboats equipped with satellite phones and Global Positioning System equipment. They are typically armed with automatic weapons, anti-tank rocket launchers and various types of grenades, according to the U.N. Monitoring Group on Somalia.

Although piracy is rampant off Somalia's lawless coast, killing crew members is relatively rare, Mwangura said. He said pirates have killed four crew members in the past 10 years.

"Normally they don't kill crew members if they cooperate," he said.

Since February, pirates have hijacked 10 ships — five have been released and five are still being held, according to the Seafarers Assistance Program.

FOX News' Nick Simeone and Jennifer Griffin, FOXNews.com's Sara Bonisteel and The Associated Press contributed to this report.

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