The Japan Coast Guard has decided to deploy two more unmanned aerial vehicles to step up surveillance activities in waters around Japan.

Coast guard officials say they plan to increase the number of large drones from the current three to five in two years.

They plan to introduce the same model as those currently deployed, which can fly more than 24 hours nonstop and send images in real time that can be viewed by ground personnel.

The addition is expected to help boost the Coast Guard's capability to patrol territorial waters and for rescue operations in case of maritime accidents.

In waters around the Senkaku Islands in Okinawa Prefecture, the number of days when Chinese government vessels were spotted in the contiguous zone just outside Japan's territorial waters last year reached a record 336.

Japan controls the islands. The Japanese government maintains they are an inherent part of Japan's territory. China and Taiwan claim them.

The unmanned vehicles are also likely to be deployed above waters off the Noto Peninsula in the Sea of Japan to detect illegal operations by foreign fishing boats.

The Coast Guard has included funding to build an operational base for the drones in its budget request for the next fiscal year that starts in April.