The South Korean navy kicked off a joint anti-submarine exercise with U.S. and Japanese forces in international waters near the Korean Peninsula, Seoul’s defense ministry announced on Monday.

The two-day drill comes after North Korean state media lashed out at the U.S. and South Korea, which it described as “war maniacs,” over the allies’ continued military exercises on and around the peninsula.

“This anti-submarine drill is designed to improve the ROK, U.S. and Japan’s ability to respond to heightened North Korean underwater threats such as its recently advanced SLBM [submarine-launched ballistic missile],” the ROK defense ministry wrote in a press