Japan on Friday named five uninhabited islands and added them to a disputed chain in the East China Sea, a move likely to spark anger from fellow claimants China and Taiwan.

The five were among the 158 uninhabited islands officially named Friday as Japan steps up protection and claims over border islands and the waters around them.

The government’s maritime policy department published a list of all of the names on its website later Friday.

The five new Senkaku islets are: Nantokojima, Nanseikojima and Higashikojima, near Minamikojima Island, and Seihokuseikojima and another islet also named Nantokojima, near Kubashima. All are now part of the Senkakus, which China and Taiwan call Diaoyu and Tiaoyutai, respectively. The chain has recently become a regional flashpoint.

The names will be used in new maps. The islets are within Japan’s established exclusive economic zone and will not change maritime boundaries.

The disputed East China Sea islands are surrounded by rich fishing grounds and potential gas deposits. Chinese Coast Guard and fishing boats have been approaching the area more frequently and sometimes violating Japan’s territorial waters, especially since Japan effectively nationalized the main islets in the chain in 2012, setting off major political turmoil.

Ties between Japan and China have worsened ever since, exacerbating friction over a contested gas field in the East China Sea and lingering animosity over Japan’s World War II invasion of China.