Kim Yo-jong accused South Korean President Yoon Suk-yeol of creating a "dangerous situation" after Seoul said that it was reviewing additional sanctions on North Korea over its recent barrage of missile tests.
The sister of North Korean leader Kim Jong-un has harshly critised South Korea's president and government for their links to the United States, state media reports.
On Thursday, Kim Yo-jong accused South Korean President Yoon Suk-yeol of creating a "dangerous situation" and comparing him unfavourably to his predecessor Moon Jae-in.
"I wonder why the south Korean people still remain a passive onlooker to such acts of the 'government' of Yoon Suk-yeol and others," she said.
The ministry said it would also consider sanctions and precautions on North Korea’s alleged cyberattacks if the North conducts a major provocation like a nuclear test.
Powerful sister in charge of diplomacy
Kim Yo-jong’s official title is a vice department director of the Central Committee of the North’s ruling Workers’ Party.
But South Korea’s spy service believes she’s the North’s second-most powerful person after her brother and handles relations with South Korea and the US.
Friday's ICBM launch was the latest in a record-breaking blitz of recent Pyongyang launches, and officials and analysts in Seoul and Washington have warned they could culminate in a seventh nuclear test.
North Korea has repeatedly said the UN sanctions are proof of US hostility toward North Korea along with its regular military drills with South Korea.