North Korea has placed several dozen combat helicopters near its sea border with South Korea, the Yonhap news agency reported on Tuesday citing South Korean government sources.

North Korea has deployed around 50 upgraded Russian-made helicopters on Baeknyeong Island in the West Sea since May.

The attack helicopters are armed with rockets and antitank missiles and are capable of carrying explosives weighing up to 500 kilograms.

The deployment appears to come in response to South Korea stationing AH-1S Cobra attack helicopters and multiple launch rocket systems on the West Sea islands.

South Korea is ready to strike back with Cheonma surface-to-air-missiles or deploy KF-16 fighter jets, the source said.