North Korean leader Kim Jong Un ordered his country to be ready to use its nuclear weapons at any time and the military to be in "pre-emptive attack" mode in the face of growing threats from its enemies, state media said on Friday. The comments, carried by the North's official KCNA news agency, marked a further escalation of tension on the Korean peninsula after the U.N. Security Council imposed harsh new sanctions against the isolated state on Wednesday for its nuclear program. North Korea, known for belligerent rhetoric, has previously threatened pre-emptive attacks on its enemies, including South Korea and the United States. Military experts doubt it has yet developed the capability to fire a long-range missile with a miniaturized warhead to deliver a nuclear weapon as far as the United States. Kim made the comments as he supervised military exercises involving newly developed rocket launchers, KCNA reported. It did not mention the date of the drills but said the new weapons had South Korea within range. South Korea's defense ministry said on Thursday North Korea launched several projectiles off its coast into the sea up to 150 kilometers (90 miles) away, an apparent response to the U.N. sanctions.

Johns Hopkins University's 38 North project, which monitors North Korea, said recent commercial satellite imagery showed new activity in the isolated country including a convoy of trucks at its satellite launch station that could be preparations for a rocket-engine test.

"One possibility is that these vehicles are returning from a delivery of supplies, fuel, or even engine components for testing to the stand," the report said. The site on the North's west coast is the upgraded rocket station where it launched a long-range rocket on Feb. 7 that put an object into space but was condemned by the Security Council as violation of past resolutions that ban the use of ballistic missile technology by the North.

On Thursday, South Korean President Park repeated a warning to the North to abandon its nuclear ambitions and said she would work to "end tyranny" by the North's leader. They were the toughest-ever comments against Pyongyang by Park, whose recent hard line against the North is a shift from her earlier policy of "trustpolitik" that focused on trying to engage in dialogue.

Last month, Seoul suspended the operation of a jointly run factory project with North Korea that had been the rivals' last remaining venue for regular interaction. North Korea's Rodong Sinmun, the official daily newspaper of the ruling Workers' Party, on Friday carried three pages of a report and photographs of leader Kim supervising the rocket launch drills.

It also ran a full page commentary insulting Park as "a wicked woman who does everything evil against the compatriots in the North."