The decision to ban free "morning-after" contraceptive pill at government health centers has enraged the population in Chile with thousands of people marching in the capital to register their protest.
About 10,000 people marched in Santiago Tuesday evening, the online edition of La Tercera newspaper said. Earlier, hundreds gathered in downtown Santiago protesting the decision with songs, skits and signs.
About 80 percent of public health workers walked off their jobs Tuesday to protest the high court ruling, sources in the sector said.
In the city of Concepcion, 500 kilometers (310 miles) south of Santiago, 12 people were arrested after protestors clashed with police, reports said.
Supporters of the ban were also on hand in central Santiago, urging the government to respect the ruling, which cannot be appealed.
The decision, taken in early April but formalized Friday, put a stop to a program started by President Michelle Bachelet, the first female president of the socially conservative country and a former pediatrician, aimed at making contraception more widely available to low-income women.
The court ruling did not ban sales of the drug in private pharmacies.