Joergen Folmer, the owner of H Folmer & Co, told the Danish Ritzau news agency that the ship with a crew of five Danish sailors had been 'captured by pirates' off the Horn of Africa. There was no immediate information on the fate of the sailors.
He said the cargo ship, which was travelling to the Kenyan port of Mombasa, had been located 240 nautical miles off the coast last Friday.
Mr Folmer said he had been informed by a French warship that it had seen the Danica White, which had been boarded by three small crafts and had armed men on board, and was heading towards the Somali capital Mogadishu.
'We asked the French warship to stop our ship. But its captain had received orders not to pursue it into Somali territorial waters,' Mr Folmer told Ritzau.
The Somali coast has recently seen a resurgence of pirate attacks which had been stopped during six months of strict Islamic rule at the end of last year.
Ethiopian and Somali troops ousted the Islamists at the start of the year.
Somalia, which lies at the tip of the Red Sea, has been without an effective government since the 1991 ouster of dictator Mohamed Siad Barre.