In Warsaw, several hundred people protested in front of the headquarters of the ruling conservative party Law and Justice (PiS) and then moved to the Constitutional Tribunal building, accusing PiS of politicising Poland's top court by manning it with judges loyal to the ruling party.
In the coastal city of Gdansk, several thousand people blocked the centre of the city, brandishing banners expressing their anger against the verdict and shouting obscenities against the ruling party.
In Lodz, nearly a thousand protesters, including feminist and left-wing activists, gathered in the city centre also venting anger against the verdict and the ruling party.
Warsaw saw yet another protest on Saturday, this time by people opposing government anti-coronavirus restrictions that on Saturday took their most severe form since the spring's first wave of the coronavirus pandemic.
The protesters, who were supported by the far-right parliamentary coalition Confederation, denied the existence of the pandemic and criticised the restriction of their freedoms. Some of them did not wear face masks or had them lowered to their chins.
On Thursday, Poland's Constitutional Tribunal ruled that laws currently permitting abortion due to foetal defects are unconstitutional. The ruling follows a 2019 motion to the court by 119 MPs from the ruling Law and Justice party and two opposition groupings.
Current abortion laws in Poland are very strict compared to other EU member countries. Abortion is admissible if pre-natal tests reveal a high probability of irreversible damage to the foetus or its affliction with an incurable and life-endangering ailment. Other admissible cases include an immediate threat to a woman's life and incest or rape. (PAP)