TOKYO (AFP) - The US military is set to deploy an unmanned spy plane in Japan to boost surveillance capabilities as North Korea apparently readied for missile launches, a newspaper report said on Saturday.

The Global Hawk will be stationed at the US airbase in Misawa, northern Japan, in the first ever deployment of the aircraft in the country, the Sankei Shimbun reported, quoting government sources.

The US military informed Japan last month about plans to deploy the plane between June and September but may bring the date forward, it said, following reports about North Korea's preparations for missile launches.

South Korea's Yonhap news agency, citing a top South Korean government official, said North Korea had loaded two mid-range Musudan missiles on mobile launchers and hidden them in underground facilities near its east coast.

The Musudan have never been tested but are believed to have a range of around 3,000 kilometres, which could theoretically be pushed to 4,000 if they were to be given a light payload.

That would cover any target in South Korea and Japan, and possibly even reach US military bases located on the Pacific island of Guam.

Tensions have soared on the Korean peninsula since December, when the North test-launched a long-range rocket.

In February, it conducted its third nuclear test and drew fresh UN sanctions.