US takes tough response on N. Korea tests

The US will bolster its ability to defend itself against North Korea, after the isolated nation had further missile tests.

The United States is deploying an advanced anti-missile defence system to South Korea as part of steps to bolster its ability to defend against North Korean ballistic missiles, the White House says.

North Korea's launching of four ballistic missiles into the sea off Japan's northwest earlier on Monday is consistent with its history of "provocative behaviour" and the United States stands with its allies against the threat, White House spokesman Sean Spicer told reporters.

"The Trump administration is taking steps to enhance our ability to defend against North Korea's ballistic missiles such as through the deployment of a THAAD battery to South Korea," he said.