North Korean leader Kim Jong Un’s influential sister has threatened South Korea for considering unilateral sanctions on the North, calling its new president and his government “idiots” and “a running wild dog gnawing on a bone given by the US”.

Kim Yo-jong’s diatribe came two days after South Korea’s Foreign Ministry said it was reviewing additional unilateral sanctions on North Korea over its recent barrage of missile tests.

The ministry said it would also consider sanctions and clampdowns on North Korea’s alleged cyber attacks – a new key source of funding for its weapons program – if the North conducts a major provocation such as a nuclear test.

“I wonder what ‘sanctions’ the South Korean group, no more than a running wild dog gnawing on a bone given by the US, impudently impose on North Korea,” Yo-jong said in a statement carried by state media.

“What a spectacle sight.”

She called South Korea’s new conservative President Yoon Suk Yeol and his administration officials “idiots who continue creating the dangerous situation”.

She said South Korea “had not been our target” when Moon Jae-in – Yoon’s liberal predecessor who sought reconciliation with North Korea – was in power.

It could be seen as a possible attempt to help foster anti-Yoon sentiments in South Korea.

“We warn the impudent and stupid once again that the desperate sanctions and pressure of the US and its South Korean stooges against (North Korea) will add fuel to the latter’s hostility and anger and they will serve as a noose for them,” Yo-jong said.

Yo-jong’s official title is 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 United States.

While it’s not the first time Yo-jong has used crude invectives on South Korea, North Korea is still expected to further escalate military tensions on the Korean Peninsula given she’s in charge of relations with South Korea and wields some influences on the North’s military, said analyst Cheong Seong-Chang, from the private Sejong Institute in South Korea.

Last month, South Korea imposed its own sanctions on 15 North Korean individuals and 16 organisations suspected of involvement in illicit activities to finance North Korea’s nuclear weapons and missile programs.

They were Seoul’s first unilateral sanctions on North Korea in five years but experts say they were largely a symbolic step because the two Koreas have little financial dealings between them.

Observers say Seoul’s push to co-ordinate with the US and others to crack down on the North’s alleged illicit cyber activities could anger North Korea and damage financing of its weapons programs.

– AAP