SEOUL - The South Korean government issued a return-to-work order for doctors on Tuesday as more doctors including medical professors join the months-long strike to protest increasing medical school admissions.

Around four percent of some 36,000 private clinics have notified the government of plans to be closed on Tuesday to take part in the protest, Health Minister Cho Kyoo-hong said.

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"To minimize the medical gap, the return-to-work order will be issued at 9 am today," Cho told a briefing.

The government previously issued a return-to-work order to striking trainee doctors before withdrawing it earlier this month as an olive branch.

According to a survey by local pollster nownsurvey conducted last week, nearly eight in 10 South Koreans oppose the doctors' strike

Under the law, doctors defying the return-to-work order can face suspension of their licenses or other legal repercussions.

READ MORE: S. Korea presses ahead with med school admissions hike despite doctor strike

President Yoon Suk-yeol said the doctors' strike was "regretful and disappointing".

"(The government) has no choice but to sternly deal with the illegal acts neglecting patients," Yoon said during a cabinet meeting, while offering to work together if the doctors return to work.

According to a survey by local pollster nownsurvey conducted last week, nearly eight in 10 South Koreans oppose the doctors' strike.

Some doctors and medical staff have openly criticized the collective action in response to the government's push for an increase in medical school admissions to address the shortage of doctors in the country.

More than half of medical professors at Seoul National University hospitals on Monday went on indefinite strike, the Yonhap news agency reported

Others have argued that increasing the number of doctors alone will do little to shore up essential services and rural areas grappling with a deepening shortage of doctors.

READ MORE: Media: S. Korea set to adjust medical reforms in bid to end walkout

More than half of medical professors at Seoul National University hospitals on Monday went on indefinite strike, the Yonhap news agency reported.

The Korea Medical Association, a leading critic of the government's reforms, has vowed to go on strike on Tuesday.

The group is also expected to stage a protest in Seoul later on the same day, calling for reconsideration of increasing medical school admissions.