North Korea said on Tuesday that its latest missile tests included a new weapons system of "great importance", while photos showed it launched a missile it had previously described as hypersonic.

North Korean leader Kim Jong Un said that the weapon's development would increase his country's readiness for war and cause its enemies "unrecoverable headaches", according to the official Korean Central News Agency, without clarifying the nature of the weapon he referred to.

Kim watched the tests on Sunday accompanied by his daughter, who is widely considered a potential heir.

The South Korean army observed on Sunday the launch of two short-range missiles by North Korea, spaced three hours apart, from the Wonsan coastal area in eastern part of the country.