A TV screen shows a file footage of the missile launch conducted by North Korea, at Seoul Railway Station in Seoul, South Korea, Thursday. (Ahn Young-Joon/AP)

North Korea fired two short-range ballistic missiles into the Sea of Japan Thursday morning, in clear defiance of U.N. resolutions, as tensions on the Korean Peninsula mount.

With the U.S. and South Korean militaries conducting huge military exercises that North Korea views as a pretext for an invasion, and new sanctions being imposed on the regime in Pyongyang, Kim Jong Un has been showing he won’t be cowed.

Two missiles were fired from Hwanghae province, south of Pyongyang, at about 5:20 a.m. and landed in the sea off the east coast city of Wonsan, South Korea’s joint chiefs of staff said. The missiles, thought to be Scud-Cs, traveled about 300 miles.

“The military is keeping close tabs on the situation and is prepared to deal with any North Korean provocations,” the joint chiefs said, according to the Yonhap News Agency.

The Japanese government lodged a protest with the North Korean Embassy in Beijing over the launch, the Kyodo news agency reported, while Defense Minister Gen Nakatani told reporters in Tokyo that Japan would stay alert. “It’s possible that they were both Scud missiles. We cannot deny the possibility of more provocative actions,” he said.

A woman passes by a TV screen showing a file footage of the missile launch conducted by North Korea, at Seoul Railway Station in Seoul, South Korea, Thursday (Ahn Young-Joon/AP)

Amid international condemnation of Pyongyang’s January nuclear test and February long-range missile launch, Kim appears to be going out of his way to show that his regime will not give in to pressure.

North Korea’s official media this week showed Kim visiting nuclear scientists and lauding their achievement in fitting a nuclear warhead onto a ballistic missile. The Rodong Sinmun, the mouthpiece of the Workers’ Party, ran a front-page photo of Kim with what it said was a miniaturized nuclear weapon.

“The right to make a preemptive nuclear strike is by no means a monopoly of the U.S.,” the Korean Central News Agency cited Kim as saying during the visit, adding that he said “if the U.S. imperialists infringe upon [North Korea’s] sovereignty and right to existence with nuclear weapons, it will never hesitate to make a preemptive nuclear strike at them.”

Last week, Kim oversaw the testing of a new 300-millimeter-caliber multiple launch rocket system. He told the military to be ready to use its nuclear weapons at any time, saying they were needed given the “ferocious hostility” of new “gangster-like” sanctions leveled against Pyongyang.

North Korea’s actions come at a tense time on the peninsula as the United States and South Korea kicked off major military exercises on Monday with 17,000 U.S. forces and 300,000 South Korean personnel.

The exercises always anger North Korea, but this year the regime’s response has been particularly vicious because the allies are practicing surgical strikes on North Korea’s main nuclear and missile facilities and “decapitation raids” by special forces targeting the North’s leadership.

This coincides with coordinated moves to punish Kim for his transgressions.

Both the United States and the United Nations have imposed tough sanctions on the North — the latter supported by China, North Korea’s main patron — and this week South Korea introduced its own unilateral sanctions. The U.N. sanctions reiterated a previous ban on North Korea conducting nuclear or missile tests.