Japan plans to launch nine satellites over the next five years in a move aimed at monitoring the world’s oceans as constant threats to its territorial integrity loom.

The satellites would help counter piracy and monitor movements of foreign ships intruding into Japanese territorial waters, the Cabinet Office said, according to The Nikkei.

They will also be used to collect data for forecasting natural disasters such as tsunamis.

The report came as Japan’s coastguard said three Chinese government ships sailed in waters around the Senkaku islands in the East China Sea, at the center of a territorial row between Tokyo and Beijing that dates back four decades.

The maritime surveillance vessels reportedly entered the 12-nautical-mile zone around Uotsurijima, one of the Senkaku islands, or Diaoyu in Chinese, the coastguard said.

Patrol ships from the two countries have constantly stirred waters near the disputed territories to challenge each others’ claims.

Tensions escalated in September when Tokyo nationalized three islands in the chain, sparking blistering anti-Japanese sentiment in across China that frayed diplomatic as well as economic relations.