TOKYO (AFP) - Japan's chief atomic energy regulator has acknowledged it was inappropriate to say it would be "much better" if North Korea dropped a missile on Tokyo rather than on a nuclear plant.

Mr Shunichi Tanaka, head of the Nuclear Regulation Authority (NRA), found himself in hot water on Thursday (July 6) after he spoke to people living near a recently restarted reactor.

"If it were me, I think it would be much better to drop (a missile) on central Tokyo," he said.

He was speaking about a possible North Korean missile attack on a nuclear facility, having reportedly been asked by an audience member what measures were in place to deal with such a strike.

An NRA spokesman told AFP that Mr Tanaka was quick to add that he was only joking.

But he later told reporters the comment was "inappropriate", the spokesman said on Friday.

Mr Tanaka had spoken in Fukui prefecture, some 350km west of Tokyo, where a nuclear reactor was restarted in May.

Japan shut down all of its dozens of reactors after a powerful earthquake in March 2011 spawned a huge tsunami that led to meltdowns at the Fukushima atomic plant, causing the world's worst nuclear accident since Chernobyl in 1986.

Reactor restarts have been controversial among people living near nuclear plants who are concerned about safety after the Fukushima disaster.

Mr Tanaka's comments came after North Korea successfully tested its first intercontinental ballistic missile on Tuesday, which landed in the Sea of Japan/East Sea.

His gaffe followed remarks last month by a Japanese prefectural governor, who said North Koreans should be "starved to death" if Pyongyang were to target his region with atomic weapons.

Mr Masanori Tanimoto, governor of Ishikawa prefecture, which sits across the Sea of Japan from North Korea, later retracted the remarks.

Municipalities across Japan have been conducting evacuation drills in response to a possible North Korean attack.

The North has previously launched multiple missiles that have fallen provocatively close to Japan.