North Korean leader Kim Jong Un wants his country to increase production of weapons-grade nuclear materials as the North conducts more and more tests of its military arsenal.

Kim made the call Monday during a meeting with scientists from the North's nuclear weapons institute, according to a report by the official Korean Central News Agency. He urged the scientists to increase production of material for nuclear weapons in order to "exponentially" expand the country's nuclear arsenal.

The KCNA report was accompanied by photos showing Kim inspecting various warheads, including a row of snub-nosed warheads dubbed "Hwasan-31" which means volcano in Korean. One of the photos showed diagrams on the wall in the background which showed how the warheads could be mounted on different types of missiles.

North Korea has conducted a series of short-range missile launches in recent days as South Korea and U.S. forces conducted a joint military exercise that Pyongyang views as preparation for an invasion of the North. KCNA also reported Monday that the military had carried out a successful test of a new underwater attack drone, plus tests of ballistic missiles that carried mock nuclear warheads.

North Korea Test-Fires 2 More Missiles as Tensions Rise

The reports of the new tests occurred just hours before the nuclear-powered U.S. aircraft carrier USS Nimitz and its battle group held joint drills with South Korean warships off the coast of the southern island of Jeju.

South Korea's Yonhap news agency said Tuesday that President Yoon Suk Yeol vowed that Seoul will not provide any financial aid to Pyongyang while it continues developing its nuclear weapons program.

Some information for this report came from The Associated Press, Reuters and Agence France-Presse.