The Japan Coast Guard on Wednesday said it detained two Filipino crew members of a Panamanian-flagged tanker suspected of murdering a Japanese sailor on the ship.
Almercito Racela, 36, and Nolieto Pabiona, 41, have admitted to killing second mate Izumi Shimba, 52, from Kyoto, around April 7.
They allegedly beat the victim and threw him into the sea from the 148,330-ton tanker Tajima as it was passing near Taiwan.
The tanker, owned by Tokyo-based Kyoei Tanker Co., is anchored at the port of Himeji, Hyogo Prefecture.
The coast guard said it found bloodstains aboard the ship, but because the incident occurred on a foreign-registered ship in international waters, the guard could not conduct an investigation.
When questioned by coast guard officials, the pair said "problems" between Shimba and themselves had led to the killing.
Coast guard investigators were asked to take the suspects into custody by the Justice Ministry, which received a request for their extradition Tuesday from the Panamanian government. Panama has jurisdiction over the ship.
The two crew members have been detained for more than a month aboard the vessel.
The coast guard said it was to hand the suspects over to the Tokyo High Public Prosecutors Office on Wednesday afternoon.
Prosecutors will next ask the Tokyo High Court for permission to hand them over to Panama. If the court gives permission, the two will be taken to Panama and tried there.
The Tajima, with a crew of 24, entered waters off the port of Himeji on April 12. While the vessel is owned, managed and operated by Kyoei Tanker, it is registered in Panama to avoid high Japanese taxes and strict shipping-control regulations.