Doctors at medical facilities across South Korea walked off the job in a one-day strike Tuesday, dramatically if briefly expanding a months-old protest against the government’s health care policies that began when residents and interns at major hospitals stopped working in February.

The physicians taking part in the one-day strike belong to the country’s biggest doctors’ group, the Korean Medical Association, which has about 140,000 members.

It was not immediately clear how many were participating, but its membership recently voted by a 3-to-1 margin in favor of collective action, according to the group.