Japanese public broadcaster NHK has said an erroneous alert warning of a North Korean missile fired at Japan was sent by a staff member who meant to file a different newsflash.
NHK denied any mechanical flaw and said on Wednesday that it is studying preventive measures.
The erroneous newsflash on Tuesday said North Korea appeared to have fired a missile at Japan and that the government was warning people to take shelter.
NHK retracted the mistake within minutes and apologised on air and on other formats.
NHK is not sure how many of its 300,000 social media followers saw the alert or notification and it is unknown if anyone followed the instructions.
Days earlier, Hawaii’s emergency authorities sent a mistaken warning of a missile attack to mobile phones across the state, triggering panic.
The erroneous NHK newsflash had been prepared for a possible emergency, the broadcaster said, adding that transmission of an alert usually involves checking by multiple staff members.
The broadcaster said most of the complaints it had received were from people who learned about the mistake when they saw the correction instead of the erroneous flash itself. Some, however, were simply trying to make sure a missile was actually not fired.
Tension has grown in Japan over North Korean missile tests as they have flown closer to Japanese coasts. NHK and other Japanese media generally alert each missile test, and the government has issued emergency notices when the missiles flew over northern Japan.
Japan is also stepping up its missile defence capabilities and is conducting missile drills across the country. Tokyo will have its first drill next week.