The director of the CIA has made an unannounced visit to South Korea as tensions in the region ratcheted up.

The visit comes after North Korea conducted another missile test on Saturday that appeared to fail shortly after launch — the third botched attempt this month. Despite the North's tests seeming unsuccessful, they have provoked hostilities with its Asian neighbours and the US.

Mike Pompeo and his wife were in the South Korean capital on Monday, an embassy official said, although they refused to say how long the visit lasted.

Trump's security adviser says North Korea will be solved 'one way or another'

The CIA chief arrived in the country over the weekend for meetings with the head of South Korea's National Intelligence Service and high-level officials in the presidential office, according to South Korean media reports.

North Korea suggested on Monday it would continue its nuclear weapons tests, saying it would build-up its nuclear forces "to the maximum" in a "consecutive and successive way at any moment".

Meanwhile, in a show of its military power, the US sent the nuclear-powered USS Carl Vinson aircraft carrier to waters off the Korean Peninsula to take part in drills with the South's naval forces.

Japan's navy dispatched its largest war ship reportedly tasked with escorting US military ships off the Japanese coast.

The helicopter carrier Izumo departed the Yokosuka port near Tokyo earlier on Monday.

Japanese media reports said it will meet up with and escort a US supply ship, a first-time mission under new security legislation that allows Japan's military a greater role overseas.

They said the US ship is expected to refuel other American warships, including the USS Carl Vinson.

Japan's Defence Ministry said only that the Izumo would participate in an international naval event in Singapore on May 15.

In pictures: North Korea military drill Show all 8 1 /8 In pictures: North Korea military drill In pictures: North Korea military drill North Korea's leader Kim Jong Un watches a military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) is seen in this handout photo by North Korea's Korean Central News Agency (KCNA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) is seen in this handout photo by North Korea's Korean Central News Agency (KCNA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video

President Donald Trump said on Saturday he would "not be happy" if North Korea carried out another missile test, adding that his Chinese counterpart President Xi Jinping would likely feel the same.

He refused to say whether this meant military action, saying: "I don't know, I mean, we'll see." He added: “We shouldn't be announcing all our moves. It is a chess game. I just don't want people to know what my thinking is.”