Amid tensions in the South China Sea, the Vietnamese Foreign Ministry warned that Chinese bombers in the waters off the disputed Paracel Islands threaten peace in the region.

“Parties bringing weapons as well as fighter jets to Vietnam’s Hoang Sa Islands (Paracel) not only violate Vietnam’s sovereignty but also complicates the situation on the East (South China) Sea,” ministry spokeswoman Le Thi Thu Hang said during a press meeting Thursday, VN Express reported reported.

Both state-run Chinese and Vietnamese media reported that the Chinese Communist Party (CCP) deployed fighter jets and at least one bomber, the H-6J to the Paracels, one of the island groups in the South China Sea where the CCP claims ownership.

Chinese Defense Ministry spokesman Ren Guoqiang late last month reported that H-6Gs and H-6Js had conducted high-intensity training in the area, including takeoff and landing exercises and long-range attacks in addition to impacting targets on the sea surface.

As Business Insider pointed out, this year, the CCP has deployed reconnaissance ships and coast guard ships in the waters off Vietnam and Malaysia.

In recent months the CCP has increased its presence in the waters of the region where over the years, it has been involved in ongoing disputes with other coastal states.

Nations like the Philippines, Taiwan, Malaysia, Brunei, and Vietnam are maintaining territorial claims against the CCP, which claims almost 1.3 square miles of their territory, reported Express UK.

Last month, U.S. Secretary of State Mike Pompeo said the CCP’s claims to the region are completely illegal. “Beijing’s claims to offshore resources across most of the South China Sea are completely unlawful, as is its campaign of bullying to control them,” he wrote in a statement.

Since the CCP took over the Paracel Islands in 1974, it has built military installations.

Vietnamese ministry spokeswoman Le Thi Thu Hang said the Hoang Sa (Paracel) and Truong Sa (Spratly) archipelagos are inseparable parts of the Vietnamese territory. She emphasized that Vietnam has a fully legal basis and historical evidence to assert its sovereignty over both archipelagos under international law.

“We call for parties to responsibly contribute to the maintenance of peace, stability, and security in the East Sea,” Hang added.