South Korea, Japan and the United States Thursday began a joint naval exercise denounced by North Korea as a "reckless provocation", The AFP reports.

Seoul's defence ministry said the two-day drill involving destroyers, supply ships and helicopters would practise humanitarian operations such as search and rescue missions. It said no live-fire exercises were planned.

But it comes at a time of rising tensions with the North following Pyongyang's failed rocket launch in April -- seen by the US and its allies as an attempted ballistic missile test.

Pyongyang said Thursday the three-nation exercise threatened to bring a "new cloud of war" to Northeast Asia.

"The North's people and military are intensely watching the trilateral military drill," said ruling party newspaper Rodong Sinmun, urging the three allies to stop "reckless provocation".

A defence ministry spokesman declined to say how many personnel were involved in the exercise in international waters south of South Korea's Jeju island, but said such drills had been held since 2008.

The US nuclear-powered aircraft carrier George Washington will join the exercise Friday before taking part in a separate drill with South Korea in the Yellow Sea from Saturday to Monday.

On land, South Korean and US forces are to hold their biggest joint live-fire exercise Friday. The aim is to showcase their "watertight defence posture and war-fighting capabilities", Seoul's defence ministry said earlier in the week.

It said 2,000 troops, F-15K and KF-16 jet fighters and light-attack planes would be among the weaponry deployed.

Four US Apache attack helicopters as well as tanks and rocket launchers will fire thousands of rounds during the drill at Pocheon near the border with the North, which marks 62 years since the start of the Korean War.

The North has taken a hostile tone with the South since new leader Kim Jong-Un took over in December, threatening "sacred war" to avenge perceived insults to Pyongyang's regime.