SEOUL - North Korea fired several short-range projectiles into the sea on Thursday, hours after the U.N. Security Council voted to impose tough new sanctions on the isolated state and South Korean President Park Geun-hye vowed to “end tyranny” by the North’s leader.

The firing escalated tensions on the Korean peninsula, which have been high since the North’s January nuclear test and February long-range rocket launch, and set the South’s military on a heightened alert.

South Korea’s Defence Ministry said it was trying to determine if the projectiles, launched at 10 a.m. (0100 GMT) from the North’s east coast, were short-range missiles or artillery fire. Chinese Foreign Ministry spokesman Hong Lei, asked about the projectiles, said China hoped all parties could refrain from actions that escalate tension. Park has been tough in her response to the North’s recent actions, moving from her earlier self-described “trustpolitik” approach, and on Thursday welcomed the move by the Security Council and repeated her call for the North to change its behaviour.

“We will cooperate with the world to make the North Korean regime abandon its reckless nuclear development and end tyranny that oppresses freedom and human rights of our brethren in the North,” Park said at a Christian prayer meeting on Thursday. Also on Thursday, South Korea adopted a long-delayed security law to set up an anti-espionage unit that was passed by parliament late on Wednesday, and another law aimed at improving human rights in North Korea.

Last month, Seoul suspended the operation of a jointly run factory project with the North that had been the rivals’ last remaining venue for regular interaction. In its latest barrage of insults against the South’s leader, the North’s official media carried a commentary on Wednesday likening Park to an “ugly female bat”, fated to “die in the dreary cave, its body hanging down”.

North Korea faces harsh new sanctions for its nuclear weapons programme under the resolution passed unanimously by the Security Council on Wednesday, drafted by the United States and backed by the North’s main ally, China.

The resolution, which dramatically expands existing sanctions, follows the North’s fourth nuclear test on Jan. 6 and a long-range rocket launch on Feb. 7, which the United States and South Korea said violated existing Security Council resolutions. The North says it was its sovereign right to launch rockets as part of a space programme to put satellites into orbit.

Moreover, the United States blacklisted North Korean leader Kim Jong Un’s right-hand man on Thursday, after U.N. Security Council voted unanimously to impose harsh new sanctions on the isolated state over its nuclear weapons programme.

Hwang Pyong So, vice chairman of the North’s powerful National Defence Commission headed by Kim, was one of several officials added to a list of Specially Designated Nationals by the U.S. Treasury’s Office of Foreign Assets Control.

Hwang, who holds the rank of Vice-Marshal in the North Korean army, heads its General Political Bureau, often seen as the most powerful position in the military after Kim, who is the supreme commander. North Korea faces tough new sanctions for its nuclear weapons programme under the resolution passed unanimously by the Security Council on Wednesday, drafted by the United States and backed by the North’s main ally China.

The U.S. Treasury added Hwang to its list along with 16 individuals who are now subject to a travel ban and asset freeze. The measures are also designed to block U.S. nationals from dealing with them. It also added O Kuk Ryol, one of a geriatric trio said to be behind North Korea’s nuclear weapons programme.

Hwang, who is in his mid-60s, is a close confidant of Kim Jong Un and has had an unprecedented rise to the top rungs of North Korea’s leadership in the space of a few years. He was associated with Kim in the late 2000s when the young man was first named in state media reports announcing his party and military credentials. He was in the Organisation and Guidance Department (OGD), a powerful and secretive body that finalises appointments within North Korea’s leading circles and rose to be its second-in-command, according to South Korea’s unification ministry.