The Chinese defence ministry on Thursday denounced flyovers by US B-52 bombers over the South China Sea and East China Sea as "provocative" actions amid soaring tensions between the two global powers.
The Pentagon said Wednesday the heavy bombers had taken part in a combined operation with Japan over the East China Sea and had flown through international airspace over the South China Sea a day before.
"Regarding the provocative actions of US military aircraft in the South China Sea, we are always resolutely opposed to them, and will continue to take necessary measures in order to strongly handle (this issue)," Chinese defence ministry spokesman Ren Guoqiang told a monthly news briefing.
China has claimed large swaths of the strategic waterway and built up a series of islands and maritime features, turning them into military facilities.
Brunei, Malaysia, the Philippines, Taiwan and Vietnam have competing claims to the region, and an international maritime tribunal ruled in 2016 that China's claims have no legal basis.
Pentagon spokesman Lieutenant Colonel Dave Eastburn said this week's flights were part of "regularly scheduled operations."
The United States rejects China's territorial claims and routinely says the military will "continue to fly, sail and operate wherever international law allows at times and places of our choosing."
"So there's nothing out of the ordinary about it, nor about our ships sailing through there."
The Pentagon chief went on to say there is no "fundamental shift in anything."