BEIJING - (UPDATE) China's navy carried out drills in the South China Sea to simulate fending off an aerial attack, state media said on Friday, as China and the United States trade barbs over who is responsible for heightened tensions in the disputed waterways.

US Secretary of State Mike Pompeo expressed concern during a visit to Beijing on Thursday over China's efforts to militarize the seas.

His remarks came after a flurry of US activity in the region, including reports last week that US Air Force B-52 bombers had flown near disputed islands that drew a sharp rebuke from China.

China's navy carried out a simulated missile attack in an unspecified area of the South China Sea using three target drones making flyovers of a ship formation at varying heights, the official army newspaper said.

The drills were part of efforts by an also unspecified training base to prepare for real-life combat against aerial targets after China's leadership said some training failed to prepare troops effectively, the paper said.

The United States and China have frequently sparred over who is militarizing the South China Sea, with Beijing blaming tensions on actions such as the "freedom of navigation" operations carried out by the US Navy.

Washington says such operations are necessary to counter China's efforts to limit nautical movement in the strategic waterway.

A US Navy destroyer sailed through waters claimed by China in May just days after the United States uninvited China from a major US hosted naval drill.

Critics have said these operations have little impact on Chinese behavior and are largely symbolic.

Pentagon officials have long complained that China has not been candid enough about its rapid military build-up and its use of South China Sea islands to gather intelligence.

PH ANALYST: VIEW IT SEPARATELY

The Philippines meanwhile should view China's missile drills as a separate move from recent reports of bullying of Filipino fishermen by members of the Chinese Coast Guard, an analyst said Friday.

Jay Batongbacal, director of the University of the Philippines Institute for Maritime Affairs and Law of the Sea said the latest missile drills is "expected" as Beijing's show of force to major superpowers.

"This kind of demonstration is really intended for major powers," he told ANC.

"I think we can take it as a separate action since they don't need to do that in order to intimidate our fishermen...The kinds of activities that are being undertaken against our fishermen are entirely different," he added.

China, Taiwan, Vietnam, Malaysia, Brunei and the Philippines all have competing claims in the South China Sea.