BEIJING — China sent warplanes into its newly declared maritime air defense zone Thursday, days after the United States, South Korea and Japan all sent flights through the airspace in defiance of rules Beijing says it has imposed in the East China Sea.

China’s air force sent several fighter jets and an early warning aircraft on normal air patrols in the zone, the Xinhua agency reported, citing air force spokesman Shen Jinke.

The report did not specify exactly when the flights were sent or whether they had encountered foreign aircraft. The United States, Japan and South Korea have said they have sent flights through the zone without encountering any Chinese response since Beijing announced the creation of the zone last week.

Shen said China’s air force would remain on high alert and will take measures to protect the country’s airspace.

While China’s surprise announcement to create the zone initially raised some tensions in the region, analysts say Beijing’s motive is not to trigger an aerial confrontation but is a more long-term strategy to solidify claims to disputed territory by simply marking the area as its own.