* Warsaw voting in referendum on firing mayor
* Mayor is a close ally of PM Donald Tusk
* Defeat for mayor would be set-back for Tusk
Residents of Warsaw were voting on Sunday on whether to fire their mayor in a referendum that has turned into a chance for voters to voice concerns about the government of Poland's Prime Minister Donald Tusk.
Although the vote is nominally about the work of Mayor Hanna Gronkiewicz-Waltz, a close Tusk ally, it has also become a lightning rod for a general sense of dissatisfaction with Tusk's government, soon to enter its seventh year in power.
The mayor's supporters are appealing to people not to vote because the results will only be valid if 29 percent or more of the city's adult residents take part. Opinion polls this week showed turnout hovering around that threshold.
In Bielany, a northern suburb of Warsaw, only a trickle of people appeared at polling stations. More were likely to arrive after morning church services, a Sunday ritual in this deeply Catholic country.
Polling stations close at 9:00 pm (1900 GMT), and results of an unofficial exit poll will be announced soon afterwards.
Pawel Sobieraj, a 47-year-old employee at a print works, said he voted to remove Gronkiewicz-Waltz.
"I don't like the way she orders Warsaw about. The referendum is an opportunity to give my opinion. She didn't do a lot of things wrong, but nobody is irreplaceable."
Other residents said they saw no point removing the mayor just a year before her term ends.
"It's just a political game. The election is next year so we could vote then. Now we have to incur needless costs," said pensioner Zygmunt Kowalski, 60.
The referendum was initiated by the mayor of a Warsaw suburb who tapped into unhappiness about a rise in bus ticket prices, roadworks that snarled up traffic, and a fumbled attempt at persuading Warsaw residents to recycle some of their garbage.
The 60-year-old mayor is deputy head of Tusk's party, a former central bank governor and one of the few women to reach the top of Polish politics.
If she is defeated, it would add to pressure on Tusk from his supporters to re-vamp his team and his policies if he is to avoid losing nationwide elections scheduled for 2015.
Tusk has so far kept faith with pro-business policies that helped the Polish economy, the biggest in eastern Europe, keep growing despite the global slump. Now, some supporters think he should start easing fiscal discipline and increase spending.