Voting opened Sunday in France for the second round of high-stake legislative elections that have already seen the largest gains ever for the country's far-right National Rally party.

French President Emmanuel Macron took a huge gamble in dissolving parliament and calling for the elections after his centrists were trounced in European elections on June 9.

The first round on June 30 saw the largest gains ever for the anti-immigration, nationalist National Rally, led by Marine Le Pen.

Sunday's vote determines which party controls the National Assembly and who will be prime minister. If support is further eroded for Macron's weak centrist majority, he will be forced to share power with parties opposed to most of his pro-business, pro-European Union policies.