North Korea said Monday that leader Kim Jong Un observed test-flights of hypersonic missiles and underscored the need to bolster the country’s nuclear war deterrent, as the country dials up weapons displays ahead of its major political conference.

North Korea fired several ballistic missiles into the sea on Sunday, just hours before South Korean President Lee Jae Myung left for China for talks expected to focus on North Korea’s nuclear programm...

This latest weapons display comes ahead of a major party congress.