Three crewmen on a pirated Japanese tugboat have been released unhurt after being held captive for a week, their employer said today.

Pirates released two Japanese seamen - 56-year-old captain Nobuo Inoue and 50-year-old chief engineer Shunji Kuroda - and a Filipino crewman who had been on the Japanese-registered tugboat, boat owner Kondo Kaiji Co said.

"We are okay," Kuroda told public broadcaster NHK by telephone from a hotel in Thailand.

"We just suffered cuts on the soles of our feet as we walked through mud of a jungle" after landing on a sand beach somewhere, he said while noting the kidnappers had not harmed them.

Kuroda said the pirates had been "very cautious" and the three crewmen had been forced to change fishing boats more than five times after being kidnapped.

Kondo Kaiji said the company would not comment on whether it paid a ransom to the kidnappers.

The tugboat Idaten was on its way from Indonesia's Batam island to Burma when the pirates kidnapped the three in the Malacca Straits seven days ago.