Voters in New Zealand are casting ballots to elect members of parliament and decide on the future of the country's voting system.

Polling stations opened at 09:00 a.m. local time Saturday and will close at 07:00 p.m. Preliminary election results are expected late Saturday.

A coalition led by the centrist National Party of Prime Minister John Key has been in power since defeating a coalition led by the leftist labor party in the last election three years ago. No party has had outright power in New Zealand since 1996, but the popularity of Mr. Key gives his party a chance to win it this time around.

A referendum attached to this year's election asks voters whether they wish to change their complicated representational voting system, in which parties get a proportion of parliamentary seats based on the share of the votes they receive. Some New Zealanders want to return to a winner-take-all format.