"I do not deny anyone the right to demonstrate to voice their views, but I think that in times of epidemic we should not do this," Kraska said on Monday, after the fifth straight day of demonstrations.
He added: "This is a biological bomb that could explode in three weeks."
Kraska warned that young people could infect their parents and grandparents after returning from rallies.
Demonstrators on Monday blocked streets in cities across Poland in the latest wave of protests against a ruling by the country's top court.
The protests erupted after a decision on Thursday by the Constitutional Tribunal that abortion of a malformed foetus violates the constitution.
The move signalled a tightening of the country’s abortion laws, which are already among the toughest in the European Union.
Gatherings of more than five people are forbidden in Poland under new rules that came into force on Saturday, aiming to limit the spread of the coronavirus epidemic.
Officials on Monday reported 10,241 new coronavirus infections and 45 more deaths, bringing the total number of cases in Poland to 263,929 and fatalities to 4,483.