The criminals boarded the 'Kenyu Maru II' before dawn and surprised the 15-person crew, the office said in a statement.

The gang of some 20 criminals tied the crew's hands and feet, then took off with their money, cell phones and the ship's communication equipment.

The Japanese ship was anchored some five kilometers (three miles) from the port of Callao, Peru's main port and part of the metropolis that includes the capital Lima.

The criminals reached the ship aboard two rowboats, the statement said. Port officials say it is the second time this year that a foreign ship was assaulted by criminals off the port of Callao.