Turnout was highest in the central Mazowieckie region, which includes Warsaw, at 54.97 percent, and lowest in the south-west Opolskie region at 43.22 percent, PKW chairman Sylwester Marciniak told reporters.
In all 18 provincial capitals participation exceeded 50 percent; Warsaw led with 58.85 percent.
Two fatalities, one arrest
Police said two elderly voters died after collapsing inside polling stations. An 84-year-old man lost consciousness in a school used as a voting site in Bielsko-Biała, southern Poland, while a woman of similar age died in Szczecin in the north-west despite emergency efforts.
Separately, officers detained a man in another Bielsko-Biała precinct for allegedly assaulting election officials; prosecutors may charge him with attacking a public servant, an offence punishable by up to three years in prison.
Polling stations close at 21:00 (19:00 GMT).
If no candidate wins more than 50 percent of valid ballots, a run-off will be held on 1 June.
(jh)
Source: PAP