Officials say striking young doctors have until the end of February to return to work or risk being punished.

South Korea’s government has given striking young doctors four days to report back to work, warning they will face indictment and suspension of medical licences if they do not return by the deadline.

The ultimatum on Monday came as about 9,000 medical interns and residents stayed off the job to protest against a government plan to increase medical school admissions by about 65 percent.

The work stoppages, which began last week, have severely hurt the operations of their hospitals, with numerous cancellations of surgeries and other treatments.

Safety Minister Lee Sang-min said chaos was mounting in hospitals and emergency services had reached a “dangerous situation” due to the strikes.

“Considering the gravity of the situation, the government issues the last plea,” he said.

“If you return to the hospital you left behind by February 29, you won’t be held responsible for what has already happened,” he said. “We urge you to remember your voice will be heard loudly and most effectively when you are by the side of patients.”

Government officials say adding more doctors is necessary to deal with South Korea’s rapidly ageing population. The country’s current doctor-to-patient ratio is among the lowest in the developed world.

The young protesting doctors say the government should first address pay and working conditions before trying to increase the number of physicians.

Vice Health Minister Park Min-soo said those who do not return to work by the end of February will be punished with a minimum three-month suspension of their medical licences.

He said they may also face further legal steps such as investigations and possible indictments.

Under South Korea’s medical law, the government can issue back-to-work orders to doctors and other medical personnel when it sees grave risks to public health.

Refusing to abide by such an order can bring up to three years in prison or 30 million won ($22,480) in fines, along with revocation of medical licences.

There are about 13,000 medical interns and residents in South Korea, most working and training at 100 hospitals. They typically assist senior doctors during surgeries and deal with inpatients.

They represent about 30 to 40 percent of total doctors at some leading hospitals.

The Korea Medical Association, which represents about 140,000 doctors in South Korea, has said it supports the striking doctors but has not determined whether to join the trainee doctors’ walkouts.

Senior doctors have held a series of rallies voicing opposition to the government’s plan.

Earlier this month, the government announced universities would admit 2,000 more medical students starting next year from the current 3,058. The government says it aims to add up to 10,000 doctors by 2035.

A public survey said about 80 percent of South Koreans back the government plan.

Critics suspect doctors, among the best-paid professionals in South Korea, oppose the recruitment plan because they worry they would face greater competition and lower income.

Striking doctors have said they worry doctors faced with increased competition would engage in overtreatment, burdening public medical expenses.