Police in Warsaw detained 37 people during a Friday protest against the tightening of Poland's abortion law, authorities in the capital said Saturday.

Warsaw authorities estimated the crowd swelled to about 100,000 participants at a time when anti-COVID-19 regulations ban gatherings larger than five. The protesters started from various points in the city, converged on a downtown roundabout and walked to the house of right-wing ruling party leader Jaroslaw Kaczynski.

They were attacked by far-right groups with firecrackers, but police contained the confrontation, Warsaw police spokesman Sylwester Marczak said.

``There was aggressive behavior on the part of soccer pseudo-fans (soccer hooligans) and also between the two sides, that's why police prevention units took action,'' Marczak said. He described the overall protest as ``very peaceful considering the number of participants.''

Noisy but disciplined marches were also held in other cities. More protests are planned next week.

Demonstrators voicing anger at Poland's conservative government and Catholic Church have assembled every day since the country's constitutional court ruled Oct. 22 to outlaw the abortion of fetuses with congenital defects.

The court preserved the provisions of Poland's abortion law, one of Europe's strictest, that permit abortions when a pregnancy threatens a woman's health or results from rape or incest.