North Korean leader Kim Jong Un on Friday told his country’s military to keep their nuclear warheads on standby and be in “pre-emptive attack” mode, local news channels reported. Kim appears to fear being targeted by enemy countries, and his aggressive move comes two days after the United Nations imposed its harshest yet sanctions on North Korea.

According to state media, Kim was supervising military exercises that included the country’s new rocket launchers when he made the statement. He also said that South Korea was within the weapons’ range.

A US defence spokesperson responded to the reports saying: “We urge North Korea to refrain from provocative actions that aggravate tensions and instead focus on fulfilling its international obligations and commitments.

On Thursday, South Korea had said its neighbour had launched several short-range missiles in seeming response to the UN’s sanctions.