SEOUL - Thousands of trainee doctors at South Korea's biggest hospitals joined a walkout on Wednesday to protest a plan to admit more students to medical school, disrupting treatment for scores of patients, health authorities said.

The government wants to increase medical school admissions from 3,000 now to 5,000 from the 2025 academic year, and then add 10,000 more by 2035, in a bid to boost healthcare in remote areas and cope with the increasing demands of one of the world's most rapidly ageing societies.

Doctors and medical students who have joined the protest, however, say South Korea has enough doctors, and the authorities should first improve pay and working conditions, especially for specialists in demanding fields such as paediatrics and emergency medicine, before recruiting more students.

Park Min-soo, a vice health minister, called on the protesters to prioritise their patients over collective action.

The protests began earlier this week, and the health ministry said that so far a total of 7,813 doctors had left their jobs, in defiance of a government order for them to stay at work. Doctors say the order is unconstitutional.

"I'd like to say once again that the basic calling of medical professionals is to protect the health and lives of the people, and any group action that threatens that cannot be justified," Park told reporters.

Due to the walk out, many hospital emergency rooms are now overcrowded, and five major hospitals in Seoul were cancelling a third to half of scheduled surgeries, local media said.

About 76% of South Koreans back the government's plan to increase the number of medical students, a Gallup Korea poll showed last week, amid concerns over an acute staff shortages in paediatrics, emergency units and clinics outside the greater Seoul area.

South Korea's population of 52 million had 2.6 doctors per 1,000 people in 2022, far below the 3.7 average for peers in the Organisation for Economic Co-operation and Development (OECD).

The Korea Interns and Residents Association, a group of doctors taking part in the protest, said they deserved better treatment including more pay.

The group also criticised the government's plan to increase the number of medical school students as a political ploy ahead of the April general election.

"We couldn't just sit back and watch medical policies built only for the sake of winning the general election. Even in a collapsing training environment, not a single resident wanted to leave the hospital," the association said in a statement.

(Reporting by Ju-min Park; Editing by Ed Davies and Miral Fahmy)