(CNN) Thousands of people marched in cities across Poland on Friday in demonstrations against plans to tighten the country's already restrictive abortion laws.

Protesters in Warsaw, many dressed in black, gathered outside parliament before marching through the capital to the headquarters of the ruling right-wing Law and Jusice (PiS) party, which is attempting to enact a staunchly anti-abortion bill for the second time in less than two years.

Poland is home to the toughest abortion laws in Europe. The procedure is only legal in three cases: if the pregnancy is the result of rape or incest, or if it endangers the life of the mother, or if the fetus is damaged. It is this third reason -- the most commonly cited -- that is the target of the latest proposals.

Pro-abortion demonstrators rally in Warsaw.

In 2016, urged on by Catholic groups, PiS lawmakers attempted to impose a total ban on abortion. But the law, which threatened to imprison women seeking the procedure, and any doctor who performed it, was scrapped after tens of thousands of people took to the streets in protest.

The same women's groups that rallied then were back out in force on Friday, protesting as lawmakers debated the revised bill entitled "Stop Abortion."