Japan's navy has dispatched its largest war ship reportedly tasked with escorting US military ships off the Japanese coast amid heightened tension on the Korean Peninsula.

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

Japanese media say the destroyer is set to escort a US supply ship in the Pacific Ocean south of Tokyo later Monday, a new mission under the new security legislation allowing Japan's military a greater role in overseas activity. The US supply ship is expected to refuel other American warships, including the USS Carl Vinson strike group, currently in the region.

Japan's defense ministry only says the Izumo left to eventually participate in an international naval event in Singapore on May 15.

It came after the US Embassy in Seoul confirmed reports America's CIA director was making an unannounced visit to South Korea, amid heightened tensions on the Korean Peninsula.

An embassy official said Mike Pompeo and his wife were in the South Korean capital on Monday, but wouldn't say for how long. He spoke on condition of anonymity because he was not authorized to speak to the media.

South Korean media reports said the CIA chief arrived in South Korea over the weekend for meetings with the head of South Korea's National Intelligence Service and high-level officials in the presidential office. The US official, however, wouldn't confirm any meetings beyond ones with officials at US Forces in Korea and the US Embassy.

The visit comes after North Korea conducted another missile test on Saturday, and a US aircraft carrier group was in nearby waters. A Japanese destroyer left port Monday, reportedly to escort US naval ships as Japan increases its military role in the region.

The Japanese destroyer Izumo, a helicopter carrier, departed from Yokosuka port south of Tokyo in the morning.

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

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 carrier strike group.

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

In Australia, Prime Minister Malcom Turnbull used a commemoration of a World War II naval battle to warn North Korea against destabilizing the region.

"Today Australia and the United States continue to work with our allies to address new security threats around the world," Turnbull said. "Together, we're taking a strong message to North Korea that we will not tolerate reckless, dangerous threats to the peace and stability of our region."

Turnbull is to meet Trump for the first time Thursday in New York.