The pirates also released a cargo ship on Thursday, and the crew of 25 Filipino men were unharmed, though held captive for two months.
Some shipping companies are beginning to use nonlethal measures to deter the pirate ships, including evasive maneuvers, electric handrails and painful sounds blasted at the pirates.
The pirates currently hold 17 ships.
Sunday is the deadline for the owners of the Saudi oil tanker, the Sirius Star, to pay a ransom of $25 million (the earlier offer of $15 million seems to be off the table.) The owners of the ship seem likely to pay the ransom.