North Korea has test-fired a tactical ballistic missile equipped with a “new autonomous navigation system”, state media said Saturday, with leader Kim Jong Un vowing to boost the country’s nuclear force.

Kim oversaw the Friday test-launch into the East Sea, also known as the Sea of Japan, on a mission to evaluate the “accuracy and reliability of the autonomous navigation system”, Pyongyang’s official Korean Central News Agency (KCNA) said.

The launch was the latest in a string of ever more sophisticated tests by North Korea, which has fired off cruise missiles, tactical rockets and hypersonic weapons in recent months, in what the nuclear-armed, UN-sanctioned country says is a drive to upgrade its defences.

The Friday launch came hours after leader Kim’s powerful sister Kim Yo Jong denied allegations by Seoul and Washington that Pyongyang is shipping weapons to Russia for use in its war in Ukraine.