North Korea test-launched two more short-range missiles Tuesday, a day after stunning the world with news it had detonated a nuclear bomb underground.
Pyongyang carried out the tests despite the threat of retaliatory action from the United Nations Security Council.
According to the Yonhap news agency in South Korea, the regime tested a ground-to-air and ground-to-ship missile from a launch pad on the east coast of the politically isolated nation.
The missiles reportedly have a range of about 130 kilometres.
The regime is also warning ships to avoid the waters off its western coast this week, a sign that more missiles tests are likely.
Susan Rice, U.S. ambassador to the United Nations, said North Korea is trying to see whether they can intimidate the international community.
"But we are united, North Korea is isolated and pressure on North Korea will increase," Rice said.
On Monday, North Korea's official news agency confirmed that the country had "successfully conducted one more underground nuclear test on May 25 as part of measures to bolster its nuclear deterrent for self-defence."
The test, North Korea's second-ever, took place near the northeastern town of Kilju. North Korea staged its first nuclear test in October 2006.
Later on Monday, the nation reportedly test fired three short-range ground-to-air missiles.
Paul Heinbecker, a former Canadian ambassador to the UN, said "not every problem has a solution" and that there is no quick fix to the tension in Northeast Asia.
He pointed out that North Korea has a massive army of more than one million people that poses a grave threat to its closest neighbour, South Korea.
"This is a very tough military situation," Heinbecker told CTV's Canada AM.
"The only thing I think that can be done is to try and contain them and make it more and more difficult for them to export materials that could fuel their nuclear program and to import equipment that they might need."
However, he acknowledged that such measures are already written into existing UN resolutions against Pyongyang, and seem to have had little effect so far.
U.S. President Barack Obama took a strong stance against the tests on Monday, saying they went against Pyongyang's own de-armament commitments.
He said the United States and the international community must "take action" in response.
France is calling for new sanctions against North Korea while Japan is backing U.S. calls for strong action against the regime.
China said it "resolutely opposed" North Korea's nuclear test.
With files from The Associated Press
