Japan has ordered aircraft to report to the US military first if they enter airspace near the main US military base in Okinawa, a report said early Saturday after fresh North Korean threats.

The transport ministry notice issued late Friday was believed to be part of precautions against possible North Korean missile launches, Kyodo News agency reported.

The order refers to airspace within 30 kilometres (20 miles) of the Kadena base where Patriot missiles have been deployed.

It comes after North Korea threatened that Japan would be "consumed in nuclear flames" if it got involved in any conflict on the Korean peninsula,

Japan, the only country ever to have suffered a nuclear attack, has authorised its armed forces to shoot down any North Korean missile headed towards its territory.

This week Patriot missile batteries were stationed around Tokyo to protect the 30 million people who live there.

In addition to the Patriots, Aegis destroyers equipped with sea-based interceptor missiles have been deployed in the Sea of Japan (East Sea) and on Friday the government said it would be permanently installing missile defences in Okinawa.

Japan official alerts N. Korean missile instead of quake
Tokyo (AFP) April 13, 2013 –

A Japanese official mistakenly announced the launch of a North Korean missile instead of sending an alert about a strong earthquake that hit western Japan on Saturday morning.

An official at the transport ministry's western Osaka aviation bureau mistakenly e-mailed 87 airport offices that a North Korean missile had been launched, the ministry said.

The official was trying to send a message to check on possible airport damage immediately after the 6.3-magnitude earthquake hit the western Hyogo prefecture, it said.

But instead of sending an e-mail about the quake, the official mistakenly dispatched a pre-prepared alert ready to go in the event of a North Korean missile launch, it said.

The incorrect message was retracted six minutes later but at least one domestic flight was delayed due to the mistake, the ministry said.

Japan is on full alert ahead of an expected mid-range missile launch by North Korea, with Patriot missiles stationed in its capital to protect the 30 million people who live there.

In addition to PAC-3 batteries, Aegis destroyers equipped with sea-based interceptor missiles have been deployed in the Sea of Japan (East Sea).

On Wednesday officials in the Japanese city of Yokohama were left red-faced after mistakenly announcing the launch of a North Korean missile to 40,000 followers on Twitter.

A 6.3-magnitude quake struck near Awaji island in the Seto Inland Sea southwest of the city of Kobe at 5:33 am (2033 GMT on Friday), Japan's meteorological agency said, injuring at least 24 people and destroying some houses.