For the second time in two weeks, the United States has deployed two aircraft carriers to the South China Sea, the US Navy said on Friday, as China and the United States accuse each other of stoking tensions in the region.

The USS Nimitz and USS Ronald Reagan carried out operations and military exercises in the contested waterway between July 4 and July 6, and returned to the region on Friday, according to a US Navy statement.

"Nimitz and Reagan carrier strike groups are...