NHK has learned that the China Coast Guard has apparently stepped up its activities near the Kinmen Islands, effectively controlled by Taiwan, since last month's fatal fishing boat accident.

Interviews with informed sources and location data sent from vessels show that at least seven Chinese ships have been navigating in or around what Taiwan calls "prohibited waters" or "restricted waters" since the accident on February 14.

Two Chinese fishers died after their boat capsized while being pursued by Taiwan's coast guard.

Location data show that seven Chinese Coast Guard ships were taking turns navigating around the islands between February 15 and Sunday.

On February 26, four vessels entered the restricted waters and sailed along the boundary of the prohibited waters that are closer to the islands.

In addition to the seven vessels, another ship believed to belong to Chinese authorities sailed into the prohibited waters.

A Taiwanese Cabinet member disclosed that five of the Chinese authority's vessels passed through these waters without permission that day.

Following the accident, the China Coast Guard has said it will step up patrolling near the islands.

The vessels' identification numbers suggest that three of the seven ships appear to be equipped with artillery. They are believed to have also entered Japanese waters near the Senkaku Islands in Okinawa Prefecture.

Japan controls the Senkaku Islands. China and Taiwan claim them. The Japanese government maintains the islands are an inherent part of Japan's territory, in terms of history and international law. It says there is no issue of sovereignty to be resolved over them.

Professor Momma Rira of Takushoku University's Institute of World Studies says China appears to be taking advantage of the accident to increase its pressure on Taiwan.

Momma also says Beijing is believed to be trying to deny the existence of the Taiwan-designated zones around the Kinmen Islands and lay claim to them itself.