The flight was first noticed by Aircraft Spots, a Twitter account that tracks aircraft and the US Air Force.
The report identified B-52s with callsigns HERO01 and HER02, which departed from Anderson Air Force Base for the South China Sea and refueled on the way from US Air Force KC-135 tankers.
The bombers drove across the Bashi Channel between Taiwan and the Philippines and flew over the South China Sea, as close as 155 miles on the coast of Guangdong Province, according to Taiwan News, the Chinese-language United Daily News quoted.
The bombers circled the Pratas Islands, also known as the Dongsha Islands, for about an hour before they set off for the Kadena Air Base in Okinawa, Japan, according to the Asia Times. The islands are controlled by Taiwan, but claimed by China.
Reports cited by Taiwan News indicate that the flight carried the bombers within reach of military targets in China. The Chinese news portal Sina said on Thursday that the B-52s were within range of Chinese radar and early warning systems as well as S-400 anti-aircraft systems imported from Russia.
The Taiwanese news site Liberty News said strategic US bombers rarely flew over waters near the Chinese coast, where Chinese military aircraft fly frequently. A spokeswoman for the US Pacific Air Force described the operation as routine.
The two B-52s deployed from Barksdale Air Force Base in Louisiana earlier this year left Guam and "passed close to the South China Sea on April 24," Captain Victoria Hight, public affairs director for the US Pacific Air Forces, Business Insider said in an e-mail late Thursday.
"The B-52Hs trained and then traveled to the United States Near Okinawa to train with the USF F-15C Strike Eagles before returning to Guam, "Hight added. Since 2004, bombing missions have routinely taken place and" the readiness of US forces to be maintained. "
Such missions, Hight said, were "in accordance with international law."
Thomas Harvey III, Deputy Defense Secretary for Strategy, Plans and Skills, told the South China Morning Post that US bombers had been deployed to protect US allies in the area.
"China has said that they want us to leave the region, we will not leave the region," he said. He added that misjudgment leading to a bigger conflict "is always a possibility if you operate in the same room militarily, we will obviously do what we can to avoid it."
Chinese Ministry of Defense spokesman Wu Qian was questioned about the US bombers at a press conference on Thursday. He said only that the Chinese forces had the situation under control.
The US bomber flight comes amidst a series of Chinese military exercises, including live fire exercises, near Taiwan, which according to government spokesmen should send a message to Taipei Taiwanese independence forces continue to do what they want. China sees the self-governing island of Taiwan as its territory.
Beijing's hostility to Taiwan has grown since Tsai Ing-wen, leader of the Democratic Progressive Party for Independence, was elected president in 2016.
Chinese planes flew through Taiwan on Thursday. The Chinese Air Force said it stole combat aircraft, early warning aircraft, reconnaissance aircraft, and H-6K bombers from several airports for "military combat exercises." The H-6K bombers had been conducting numerous drills in Taiwan since April 18 to "enhance their ability to protect national sovereignty and territorial integrity."
An editorial published Friday by the Chinese tabloid Global Times said that if the American bomber flight sent a message to Taiwan about Taiwan, it would not work.
"The US can not prevent the mainland from putting military pressure on Taiwan," it said. "If the Taiwanese authorities openly propagate Taiwan's independence policy and break off all official contacts with the mainland, the mainland will see Taiwan as an enemy regime and has endless means to deal with it."