The Japan Coast Guard is on maximum alert ahead of the Group of Seven Summit that is scheduled to kick off on Friday in the western city of Hiroshima.
The coast guard says nearly 100 patrol boats from across the country will be sent to guard the summit venue, which is located on a small island.
In addition, the SeaGuardian, the US-made surveillance drone, which Japan started using last year, is currently keeping watch around the clock above the hotel where the leaders will meet.
Coast Guard Commandant Ishii Shohei told reporters on Wednesday that maritime security will be crucial because the leaders are scheduled to travel sometimes by ship.
He added that the coast guard will work closely with the police and security authorities to ensure that the summit events go smoothly.
The coast guard is asking operators of fishing boats and passenger vessels not to enter a roughly 300-meter zone around the hotel through Monday.
It has also designated the waters around Hiroshima Port as an area that cannot be entered without permission.
Coast guard officers are also patrolling port facilities to prevent suspicious items from being brought in.