Official results are still being tallied, but Japanese public broadcaster NHK said Abe's ruling coalition had secured a two-thirds majority in Parliament's Lower House, winning 326 of 475 seats.

And the White House offered congratulations to Abe and his Liberal Democratic Party for their success at the polls.

The win gives Abe four more years to institute his policies aimed at reviving Japan's economy by flooding the market with cash, encouraging corporations to create more jobs and increasing government spending.

Japan unexpectedly slipped into a recession this year, dealing a blow to Abe's much-vaunted "Abenomics" stimulus and economic reform package.

On Sunday, Abe thanked voters for their support and said the election results are a mandate from the Japanese people to stay the course and keep pushing ahead.

READ: Why Abe wants an election

Strange timing

An election wasn't actually required until late 2016. And many had wondered why Abe, with a sizable majority in the Lower House -- 295 out of the 475 seats -- would risk ceding power so early.

Before the vote, E. Keith Henry, analyst and founder of Asia Strategy, a Tokyo-based government policy consulting group, said he found the timing "puzzling."

"Why call an election when you have such a dominant position?" he asked.

READ: Abe's election gamble puts policies on the line

But as exit poll results came in on Sunday, it appeared that Abe's coalition had picked up more than 30 seats. Winning a two-thirds majority in the Lower House gives the party a chance to propose amending the Constitution and enact bills the Upper House rejects, NHK reported.

Controversial reforms

While a key component of Abenomics has been extra government spending, a sales tax hike this year and rising costs have taken their toll on small businesses and their customers.

In a bit to boost his election fortunes, Abe delayed a sales tax hike planned for October 2015. His special adviser on economic affairs, Etsuro Honda, has called for a further $25 billion in cash handout stimulus and tax cuts to kickstart the economy.

But that hasn't satisfied all voters.

"Abenomics is no good at all," said Shuichi Kobayashi, the fourth-generation owner of a 100 year-old tofu shop in Tokyo.

He said the recent economic conditions are a threat to his livelihood.

"Our life is getting tough."

READ MORE: Is Abenomics working? Depends who you ask

CNN's Andrew Stevens, Naomi Ng, Anna Maja Rappard and Catherine E. Shoichet contributed to this report.