North Korea fired multiple cruise missiles off its east coast on Wednesday as its rivals South Korea and the United States held joint military exercises, the South Korean military said.

The missiles were fired at around 10:15 a.m. (0115 GMT) from its South Hamgyong province, South Korea's Joint Chiefs of Staff (JCS) said.

It was not immediately clear how many projectiles were fired and exactly what type they were.

The test launch took place three days after North Korea fired a short-range ballistic missile towards the sea off its east coast.

Pyongyang has long bristled at exercises conducted by South Korean and U.S. forces, saying they are preparation for an invasion of the North, and it fired the missiles into the sea as the drills were underway.

South Korea and the United States reject North Korea's claims and say the exercises are purely defensive.

The military was on high alert and South Korean and U.S. intelligence authorities were analyzing details of the missiles, the JCS said.

South Korea's Yonhap news agency said Wednesday's launches could have involved the North's strategic cruise missiles.

"Strategic" is typically used to describe weapons that have a nuclear capability. North Korea's last known firing of its strategic cruise missiles was on March 12 when it said it fired two of them from a submarine.

The allies are set to conclude 11 days of the exercises, called "Freedom Shield 23," on Thursday.

"We will successfully wrap up our Freedom Shield exercise as planned under firm combined defense posture," the military said in a statement.

Separately on Wednesday, the USS Makin, an amphibious assault ship, docked in South Korea for the allies' first large-scale amphibious landing exercise in five years, the U.S. military said.

South Korean President Yoon Suk Yeol, meanwhile, visited the military cyber command and called for proactive operations to defend against cyber threats, his office said.

North Korea has been ramping up its military tests in recent weeks, firing an intercontinental ballistic missile last week and conducting what it called a nuclear counterattack simulation against the United States and South Korea over the weekend.

It has also been strong on rhetoric against the United States and South Korea. A North Korean foreign official said pressure to give up nuclear weapons was tantamount to declaration of war, state KCNA news agency said on Wednesday.

The remark was directed at U.S. Ambassador to the United Nations, Linda Thomas-Greenfield, who said on Monday it was time for North Korea to "abandon its unlawful WMD and ballistic missile programs in a complete, verifiable, and irreversible manner," referring to Weapons of Mass Destruction.