Taiwan has taken fighter jets into the air to scare off Chinese planes entering its air defense identification zone.

Among these planes were bombers that flew south of the island and then left for the Pacific Ocean. The incident was a new surge in tension and the largest invasion since the end of May.

Taiwan, which China considers part of its territory, has complained over the past two years or so about repeated Chinese Air Force operations near the democratically controlled island, often in the southwestern part of its air defense identification zone, near the Taiwan-controlled Pratas Islands.

Taiwan calls China’s repeated military actions near the island a war in the “gray zone,” designed both to exhaust the Taiwanese forces, regularly forcing them to take them into the air, and to test Taiwan’s reaction.

The latest Chinese mission included 17 fighter jets and six H-6 bombers, as well as electronic warfare, early warning, anti-submarine aircraft and tanker aircraft, Taiwan’s Defense ministry said.

Some planes flew over the area northeast of the Pratas Islands, according to a map provided by the Ministry.