ANP said the hijackers, who are demanding a ransom for the crew consisting of four Russians and five Filipinos, claim the Dutch vessel, the Amiya Scan, was fishing in Somali waters.
A spokesman for Reider Shipping, the ship's owners, said the claims were "nonsense" since the vessel is a cargo ship delivering drilling platform components and not a fishing trawler.
The vessel, sailing under the flag of Antigua and Barbuda, was seized by Somali pirates in the Gulf of Aden on May 26. Local authorities reportedly deployed forces last Wednesday to mount a rescue operation.
Russia's Foreign Ministry urged Somali authorities on Thursday not to take any action that could jeopardize the safety of the crew members.
"Russia urges Somali authorities to refrain from any action that could put the lives of the crew in danger," the ministry said in a statement.
The waters off the east African nation are considered among the most dangerous in the world for pirate attacks.
