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

China’s air force on Thursday 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 military aircraft. The United States, Japan and South Korea have said they have sent military or coast guard flights through the zone without encountering any Chinese response since Beijing announced its creation last week.

Shen described Thursday’s flights as “a defensive measure and in line with international common practices.” He said China’s air force would remain on high alert and will take measures to protect the country’s airspace. Chinese officials have said commercial flights are unaffected by the new rules.

While China’s surprise announcement last week announcing 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.

China’s lack of efforts to stop the foreign flights — including two U.S. B-52s that flew through the zone on Tuesday — has been an embarrassment for Beijing. Even some Chinese state media outlets suggested Thursday that Beijing may have mishandled the episodes.

“Beijing needs to reform its information release mechanism to win the psychological battles waged by Washington and Tokyo,” the Global Times, a nationalist tabloid published by the Communist Party’s flagship People’s Daily, said in an editorial.

Without prior notice, Beijing began demanding Saturday that passing aircraft identify themselves and accept Chinese instructions or face consequences in an East China Sea zone that overlaps a similar air defense identification zone overseen by Japan since 1969 and initially part of one set up by the U.S. military.

But when tested just days later by U.S. B-52 flights — with Washington saying it made no effort to comply with China’s rules — Beijing merely noted, belatedly, it had seen the flights and taken no further action.

South Korea’s military said Thursday its planes flew through the zone this week without informing China and with no apparent interference. Japan also said its planes have been continuing to fly through it after the Chinese announcement.