In the capital, protesters gathered near the home of Jarosław Kaczyński, head of the governing conservative Law and Justice party. They brandished signs saying “We want to have a choice!” and “You’re going to do jail time.”
Warsaw police said that stones were being thrown at officers, adding that some of the demonstrators "clearly want to cause to an open conflict".
Protests were also being staged in other Polish cities, including Poznań, Łódź, Wrocław and Kraków, state news agency PAP reported.
The demonstrations were sparked by a ruling from Poland's Constitutional Tribunal on Thursday which heralded a tightening of the country's abortion laws, already among the toughest in the European Union.
The court decision caused anger among women’s rights activists and leftist groups, but was welcomed by anti-abortion campaigners and many conservatives.
Police stand guard amid a protest near the home of Poland’s conservative leader, Jarosław Kaczyński, in Warsaw on Friday. Photo: PAP/Leszek Szymański
After the ruling comes into effect, abortions will only be allowed in Poland if a pregnancy is the result of a crime such as incest or rape, or threatens the life or health of a woman.
Since the conservative Law and Justice party came to power in late 2015, there have been appeals for a blanket ban on all abortions in Poland, and calls to penalise doctors who perform such operations and women who terminate pregnancies.
Proposals for tighter laws previously triggered extensive street protests, and the government has so far shied away from toughening abortion rules.