Recent activity by China’s strategic bombers in the South China Sea’s Paracel Islands seriously violated Vietnam’s sovereignty over the disputed territory, Vietnam’s Foreign Ministry said on Monday. The flights increase tensions and cause regional instabilities, Foreign Ministry spokeswoman Le Thi Thu Hang said. The Philippines also expressed “serious concerns” on Monday over the presence of the bombers in the area, Reuters said. Vietnam and China have long been embroiled in maritime disputes in the sea. The Philippines, Malaysia, Brunei and Taiwan also have claims to parts of the potentially energy-rich maritime territory. China’s Foreign Ministry spokesperson Lu Kang said Monday that moving the bombers into the area was “part of the normal training for the Chinese military,” adding that the US “sending its own warships and planes to the region… poses a danger to other countries.”