Pyongyang launched at least seven missiles on Monday evening in what some analysts believe is an attempt to gain U.S. attention.

The launch, into waters west of Japan, came shortly after the United States and South Korea criticized the North for sending troops to join Russia’s war.

South Korea’s Joint Chiefs of Staff said North Korea could have tested a new, solid-fueled long-range ballistic missile. Missiles with built-in solid propellants are easier to move and hide and can be launched quicker than liquid-propellant weapons.