A U.S. spy plane conducting a routine patrol over international waters in the East China Sea on Tuesday was intercepted by two Chinese fighter jets.

U.S. military officials in the Pacific told Reuters that one of the Chinese planes came within “an unsafe excessive rate of closure” to the U.S. aircraft, but blamed the incident on “improper airmanship, as no other provocative or unsafe maneuvers occurred.”

The altercation underscores the geopolitical power struggle in maritime Asia between the U.S. and China. Beijing has claimed most of the contested reefs, rocks and islets of the South China Sea as its own territory. But Vietnam, the Philippines, Malaysia, Taiwan and Brunei have competing claims to various parts of the region.

Beijing responded to the incident by accusing Washington of “deliberately hyping up the issue of the close surveillance of China by U.S. military aircraft,” according to a statement quoted by Reuters.

“Chinese military pilots consistently carry out operations in accordance with the law and the rules, and are professional and responsible,” China’s Defense Ministry said.

The U.S. Department of Defense said in a statement it was addressing the issue with Beijing.

The incident is not without precedent. On at least two occasions in the last year — once in September 2015 and again last month — Chinese jets came dangerously close to U.S. aircraft over Asian waters.

[Reuters]