North Korea said it fired two cruise missiles from a submarine and issued a new threat to “mercilessly punish” the United States as it starts large-scale military drills with South Korea that have stoked Pyongyang’s anger.

South Korea’s joint chiefs of staff said the military was on high alert and the country’s intelligence agency was working with its US counterpart to analyze the specifics of the launch, according to the Guardian.

The missile test took place about 24 hours before the United States and South Korea’s joint forces started their annual 11-day military exercises, dubbed as the “Freedom Shield 23,” planned to be the biggest war games since 2017.

At a briefing on March 13, U.S. State Department spokesperson Ned Price directly linked the expanded drills with the increased provocations by North Korea, whose official name is the Democratic People’s Republic of Korea.

“Unfortunately, the DPRK has put us in a position to have to reinforce, in tangible ways, the security commitment that we have,” Price said.

“They have made the security environment in Northeast Asia and the broader Indo-Pacific region all the more dangerous, all the more threatening to our deployed troops, to Americans in the region and, of course, to our key allies in ROK,” he added, using an abbreviation for the official name of South Korea. At a briefing on March 13.

“They have made the security environment in Northeast Asia and the broader Indo-Pacific region all the more dangerous, all the more threatening to our deployed troops, to Americans in the region and, of course, to our key allies in ROK,” he added, using an abbreviation for the official name of South Korea, according to VOA.

The United States and South Korea are preparing to hold their Freedom Shield exercises from March 13-23, which are designed to bolster their defenses against North Korea’s nuclear and missile threats, according to gCaptain.