Ryu and Park say the junior doctors, a crucial cog in South Korea's highly regarded medical system, are overworked, underpaid and unheard.

Hospitals have turned away patients and cancelled surgeries after about two-thirds of the country's young doctors walked off the job this month in protest.

The young doctors say their pay and working conditions should be the priority, rather than the government's plan to boost the number of physicians.

"The current medical system in South Korea, which is a great one, is run by making cheap trainee doctors keep grinding," Ryu, 25, told Reuters.

Senior doctors and private practitioners have not walked out but have held rallies urging the government to scrap its plan, with 400 gathering in Seoul on Sunday.

But the government's plan to boost medical school admissions is popular, with about 76% of respondents in favour, regardless of political affiliation, a recent Gallup Korea poll found.

Ryu said he worked more than 100 hours a week at one of the country's most prestigious university hospitals, for 2 million won to 4 million won ($1,500-$3,000) a month including overtime pay. A first-year U.S. resident averages about $5,000 a month, according to American Medical Association data.

Hospitals have not processed the resignations of the protesting doctors, who say they are not on strike. The government has ordered them back to work, threatening to arrest them or revoke their licenses, saying their collective action cannot be justified and people's lives must come first.

Park and other doctors say the order is unconstitutional, forcing them to work against their will.

The doctors on walkout represent just a fraction of South Korea's 100,000 doctors, but they can make up more than 40% of staff at large teaching hospitals, performing crucial tasks in emergency rooms, intensive care units and operating rooms.