The Japan Coast Guard will deploy two large patrol vessels to areas of the Sea of Japan to reinforce protection of nuclear power plants against terrorism, sources familiar with the matter said Saturday.

Two new 1,500-ton vessels with helipads will be deployed between fiscal 2019 and 2020 to the coast guard's Tsuruga office in Fukui Prefecture where several nuclear plants are located, according to the sources.

Patrol boats of similar size, each costing about 6 billion yen ($54 million), will be introduced in other parts of the country in the future, they said.

The government is moving to strengthen counterterrorism measures in the run-up to the 2020 Tokyo Olympics and Paralympics, in line with an agreement in February with the International Atomic Energy Agency to bolster Japan's capacity to respond to nuclear terrorism.

The coast guard expects the new ships will also enhance its ability to respond to North Korean boats engaged in illegal fishing, and to unidentified ships sighted off the central Japan coast, the sources said.

The new ships could also be used to respond to emergency situations at nuclear plants in other areas, and crew will receive special training in dealing with radioactive substances, they said.

An additional 60 to 80 coast guard crew will be posted at the Tsuruga office, nearly doubling the personnel there.

The Tsuruga office belongs to the 8th Regional Coast Guard Headquarters, which is responsible for patrolling waters along a 2,000-kilometer stretch of Japan's central and western coasts. That office operates three patrol boats, the largest being the 350-ton Echizen.

To better deal with China's growing maritime assertiveness, Japan has allocated an initial budget of a record 211.2 billion yen to the Japan Coast Guard for fiscal 2018.