Hundreds of people demonstrated noisily in the streets of Madrid Saturday to protest new cuts restricting free health care for immigrants who do not have full legal status in Spain.
Seven of Spain's 17 regional health authorities have already said they will refuse to implement the measure and many doctors and nurses have insisted they will continue to treat those excluded by the change.
Rights groups Medecins du Monde (Doctors of the World) and Amnesty International have also denounced the new measure as a violation of basic rights.
Previously, such immigrants had access to free care in the public health system. From Saturday however only children, pregnant women and people needing emergency medical care will be eligible.
Conservative Prime Minister Mariano Rajoy's government introduced the new restrictions as part of its austerity programme to tackle the country's debt crisis.
But an Internet petition for Spanish health professionals, which vows to stand by those affected by the change, has already attracted 1,885 signatures.
"My loyalty towards my patients does not allow me to fail in may ethical and professional duty ...," says the online manifesto.
A joint statement by the Spanish branches of Amnesty International, Doctors Without Borders and other rights groups, also attacked the new measures.
They warned that the cuts "...could cost lives, because they will leave thousands of people without access to the health system".
Among those marching in Madrid were health professionals, but also some of those hit by the change.
"This is an act of rebellion against a totally unjust law," 51-year-old Peruvian Rodrigo Rojas, told AFP.
Rojas said he had come to Spain 15 years ago and set up his own construction firm, which folded in 2009 when the country's property market collapsed.
Suddenly without a job, he had his residency permit withdrawn and he now found himself among the thousands denied full access to free health care.
"Immigrants have in their time been a cheap source of labour, and now that they are no longer of any use, they are being sent to the slaughterhouse," he said.
One placard carried by a protester denounced what it described as "health apartheid".
Other Spanish cities also hosted demonstrations.