Australia¡¯s conservative government failed to win any of the five by-elections held this weekend, defeats widely seen as an indication Prime Minister Malcolm Turnbull faces an uphill battle to be re-elected in a national poll due by May 2019.

¡°We will look very seriously and thoughtfully and humbly at the way in which the voters have responded,¡± Turnbull told reporters in Sydney on Sunday.

In what was coined ¡°Super Saturday,¡± voters in five seats went to the polls after a handful of Labor opposition lawmakers were forced from office after falling foul of the country¡¯s constitution that bans politicians from elected office if they are dual citizens.

The Australian Electoral Commission (AEC) early on Sunday said the five seats were all won by Labor, dealing a blow to Turnbull, who is under pressure to demonstrate a viable pathway for re-election with his coalition badly trailing Labor in opinion polls.

Political analysts say Turnbull must win marginal seats in the state of Queensland, traditionally a conservative heartland, if he is to be re-elected.

But his government failed to win a key by-election seat in Queensland on Saturday, despite support from Australia¡¯s powerful right-wing party One Nation.

The AEC said Labor retained the Queensland seat of Longman with a bigger majority than it had secured in 2016.

Failure to win at least one seat at the by-elections means Turnbull will continue to struggle to pass legislation with only a one-seat majority.