A Maritime Self-Defense Force destroyer on antipiracy patrol off Somalia last week helped a Malta-registered ship being approached by a suspicious vessel, the Defense Ministry said.

The Samidare received a radio call from the Maltese ship shortly after 3 p.m. Saturday Japan time and then drove away the suspicious ship by sounding a warning and dispatching a patrol helicopter, the ministry said.

The 4,550-ton Samidare and 4,650-ton Sazanami have been patrolling against pirates since late last month to protect Japan-linked ships, including Japanese-registered vessels, foreign registered ships with Japanese nationals or shipments on board and other boats operated by Japanese firms.

The Maltese ship was not in the categories stipulated under the maritime police-action provision of the Self-Defense Forces Law. But a rescue operation poses no problems because it constitutes a humanitarian step based on the law of the sea, the ministry said.

Earlier this month, the Sazanami also scared away a suspicious boat approaching a Singapore-registered freighter.