The Netherlands voted Wednesday in a provincial election that will decide who sits in the Senate, a key poll that could paralyze premier Mark Rutte's ability to pass reforms.

More than 12.7 million citizens can vote across the Netherlands, with the 570 officials who win to decide in May who sits in the Dutch upper house for the next four years, well into the next government's mandate.

The ruling coalition of Rutte's Liberal VVD and the PvdA Labor party currently relies on the progressive D66 and two small Christian parties to secure a 38-seat majority in the 75-seat Senate.

But opinion polls predict that the PvdA will have fewer Senate seats, forcing the coalition to seek support from other opposition parties to pass laws, possibly in exchange for concessions on reforms.

The Senate composition that emerges will also be crucial to the next government -- whether voted in at elections scheduled for 2017 or if the cabinet collapses before then.

"It's important to vote today because even if the Senate isn't elected directly it represents our voices and passes laws," said student Joshua, 18, as he voted in The Hague.

Support for Rutte's People's Party for Freedom and Democracy (VVD) appears unwavering, despite a series of scandals including over a deal made with a drug baron 15 years ago which last week forced the resignation of VVD justice minister Ivo Opstelten and his deputy Fred Teeven.

Despite his headline-grabbing anti-Islam rhetoric, Geert Wilders is not expected to play an important role in the polls as he is still considered politically toxic after bringing down the government in 2012.

"I hope the Dutch will vote decisively against populist movements," said train conductor Ton, 52, casting his vote in The Hague's main train station.

Turnout for provincial polls is traditionally low, standing at 46 percent in 2007 and 56 percent in 2011, compared with more than 74 percent in the 2012 national elections.

Polls close at 2000 GMT, with the winners to decide on the Senate's makeup on May 26. (+++++)