In a special address published on social media, Kaczyński - the head of the governing conservative Law and Justice party - warned that demonstrators taking to the streets amid an escalating COVID-19 epidemic were “bringing about a general danger, and thus committing a serious crime."
“We have to defend Polish churches, we have to defend them at all cost,” Kaczyński said, after five straight days of demonstrations against a court ruling which signalled a tightening of the country’s abortion laws.
Further protests were underway on Tuesday evening.
Kaczyński added: “This attack aims to destroy Poland, to lead to the triumph of forces whose power will in fact end the history of the Polish nation, as we have perceived it so far, of this nation which is our nation, which we have in our minds and hearts.”
His address was made public on a day that Poland reported a record rise in coronavirus infections.
Kaczyński warned that the demonstrations, in defiance of rules that ban large gatherings amid the epidemic, “will certainly cost the lives of many people.”
The street protests were sparked by a decision on Thursday by the country’s Constitutional Tribunal that abortion of a malformed foetus violates the constitution.
Activists opposed to tightened abortion rules have staged protests during church services in Warsaw and other Polish cities, spray-painting slogans on the exterior walls of church buildings.
Parliamentary security guards were called in to the Polish lower house on Tuesday after a protest in the chamber by left-wing MPs opposed to stricter abortion laws.
Poland on Tuesday confirmed 16,300 new coronavirus infections, the most since the pandemic hit the country in early March.