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The Chinese government said on Wednesday that it detected and monitored flights by two unarmed American B-52 bombers over a disputed part of the East China Sea on Tuesday, but that it took no action.

The two American B-52 bombers flew through territory that was part of China’s newly-declared maritime air defense zone, where it has demanded planes register their flight plans and communications frequencies with Beijing even though Japan claims sovereignty over the area. The American aircraft did not identify themselves, the Associated Press reports. The Chinese Defense Ministry released a statement on Wednesday saying it had detected and monitored the flights for more than two hours. “China has the capability to exercise effective control over the relevant airspace,” the statement said.

During a briefing in Beijing, China’s Foreign Ministry said that its muted reaction was in accordance with rules announced by the Defense Ministry, and that its response to foreign aircraft in the zone in the future would depend on how large the threat is, the New York Times reports.

The U.S. military said that the flights were a training mission and not a response to China’s latest assertion of authority over the zone.

[AP]