Image copyright Missile Defense Agency Image caption A 2016 flight test of a ground-based interceptor is launched from Vandenberg Air Force Base

The US has for the first time successfully tested its defence system against an intercontinental ballistic missile (ICBM), say officials.

A ground-based interceptor was launched at a California air base and shot down a mock ballistic missile, the Missile Defense Agency (MDA) said.

The Pentagon said the test was long-planned but it comes amid increased tensions with North Korea.

The test comes after Pyongyang fired its ninth missile this year.

MDA Director Vice Adm Jim Syring called the test a "critical milestone".

"This system is vitally important to the defence of our homeland, and this test demonstrates that we have a capable, credible deterrent against a very real threat," he said on Tuesday.

It was the first live-fire test against a simulated ICBM for the Ground-Based Missile Defense (GMD).

Media playback is unsupported on your device Media caption How do you solve a problem like North Korea?

The interceptor, which was launched from Vandenberg Air Force, collided with a simulated missile launched from Kwajalein Atoll in the Marshall Islands over the Pacific Ocean, the agency said in a news release.

The announcement comes in the wake of North Korea's third missile test in three weeks.

The Scud flew about 450km (280 miles) before landing in Japanese waters, prompting Japan to lodge a protest.

Pyongyang has repeatedly defied a UN resolution banning all nuclear and missile activity, and has ramped up the pace of its tests in recent months.

President Donald Trump joined South Korea and Japan in condemning the test.

"North Korea has shown great disrespect for their neighbor, China, by shooting off yet another ballistic missile...but China is trying hard!" he tweeted on Monday.