A teacher has fatally stabbed an eight-year-old girl at an elementary school in South Korea, in an incident that has shocked the nation.

The female teacher, who is in her 40s, confessed to stabbing the student in the central city of Daejeon, police said.

The girl was found with stab wounds on the second floor of a school building at 18:00 local time (09:00 GMT) on Monday and was pronounced dead at hospital. The teacher was found beside her with stab wounds that police said may have been self-inflicted.

South Korea’s acting president Choi Sang-mok ordered an investigation into the case on Tuesday and urged authorities to “implement necessary measures to ensure such incidents never happen again”.

Some locals laid flowers and a stuffed doll at the gate of the school, which was closed on Tuesday.

In a police briefing, Yook Jong-myung, head of the Dajeon Western Police Station, said the teacher was currently recovering in hospital, adding that she had a wound on her neck that had been stitched.

The Daejeon education office earlier said the teacher had requested a six-month leave of absence citing depression on 9 December, but had returned to school just 20 days later after a doctor assessed her as being fit to work.

During her time off she had suicidal thoughts, Mr Yook said, citing testimony the teacher had provided to police.

Days before the stabbing, the teacher had displayed violent behaviour, including putting another teacher in a headlock, the education office said.

Two officials from the education office had visited the school on Monday – the morning of the stabbing – to investigate that earlier altercation.

After the attack on the co-worker, the education office recommended that the teacher be put on leave and be separated physically from the other teacher.

She was made to sit beside the vice principal’s desk so that she could be kept under close watch.

She had also not been teaching any classes since her leave in December, and did not have any contact with the eight-year-old student, the official said.

According to the testimony given by the teacher to police, she was “annoyed” that she had not been able to return to teaching a class.

She told them she had purchased a weapon on the day of the attack and brought it to school – adding that she had planned to kill herself along with a child.

The testimony went on to say that the teacher did not care which child it was, and targeted the last to leave. She managed to “lure the child into the media room” before attacking them, it said.

The student was reported missing on Monday evening, after a bus driver informed the school that she had not arrived to be picked up that day.

South Korea is a generally safe country with strict gun control laws. But in recent years, it has grappled with several high-profile crimes, including stabbings.

“It pains me to see such incidents because a school should be our safest space,” said acting President Choi. “I offer my deep condolences to the victim’s family who suffered great shock and agony.”