U.S. bombers entered the East China Sea air-defence identification zone, not prepared for defence and without notifying China.
According to The Wallstreet Journal which is quoting U.S. officials, a pair of B-52 bombers flew over disputed islands in the East China Sea without informing Beijing. This can be seen as a direct challenge to China and its establishment of its recently declared air-defence zone.
[Chinese source: Global Network 环球网—国际新闻 on November 27, 2013]
According to another Chinese news service, referring to U.S. officials and a Washington Times article, both B-52 bombers should have taken off at Guam airbase and entered China's air-defence zone on November 25 at about seven o'clock in the evening. They carried no weapons and were not accompanied by any fighter escort.
[Chinese source: Tencent News 腾讯新闻, an internet news service in People's China, on November 27, 2013]
At the time this blogspot came into being, there were no official Chinese comments available on the incident.