Israelis began voting Tuesday in a high-stakes election that will decide whether to extend Prime Minister Benjamin Netanyahu's long right-wing tenure despite corruption allegations or to replace him with an ex-military chief new to politics.

The vote is expected to be close and likely lead to frantic negotiations to form a coalition government once results are in, with opinion polls having shown Netanyahu best placed to do so.

Polls opened at 0400 GMT and were to close at 1900 GMT in most areas, with final results not expected until early Wednesday.

Ex-military chief Benny Gantz has mounted a strong challenge to the veteran prime minister by brandishing his security credentials while pledging to undo damage he says Netanyahu has inflicted on the country with divisive politics.

The election will be in many ways a referendum on the 69-year-old leader who has built a reputation as guarantor of the country's security and economic growth, but whose populism and alleged corruption have left many ready for change.

He has engaged in populist rhetoric throughout the acrimonious campaign that critics say amounts to the demonisation of Arab Israelis and others.

True to form, Netanyahu issued a deeply controversial pledge only three days before the election, saying he planned to annex settlements in the occupied West Bank should he win.

Extending Israeli sovereignty on a large-scale in the West Bank could be the death knell to already fading hopes for a two-state solution with the Palestinians.

It is a move long-sought by Israel's far-right.

'Need for change'

Netanyahu has also sought to portray himself as Israel's essential statesman, meeting with his close ally US President Donald Trump, Russian President Vladimir Putin and Brazilian President Jair Bolsonaro in the run up to the vote.

He has highlighted Trump's recognition of Jerusalem as Israel's capital and of Israel's claim of sovereignty over the Golan Heights, while also saying the US leader is aware of his annexation plans.

"Who else can do this? Who can do this? Come on. Honestly," Netanyahu said in an interview on Sunday with local news site Arutz Sheva.

"Who can stand in front of the world? Who can stand in front of the American Congress? Who can move public opinion in that direction?"

At the same time, he has used Trump-like tactics, calling the corruption investigations a "witch hunt" and denouncing journalists covering them.

On Monday night, he paid a visit to Jerusalem's Western Wall for a last-minute prayer.

Gantz, a 59-year-old former paratrooper who has formed a centrist alliance to challenge Netanyahu, has invoked the corruption allegations against the premier to make his case that it is time for him to go.

He has called Netanyahu's annexation pledge an "irresponsible" bid for right-wing votes.

As for his position on the issue, Gantz says he favours a "globally backed peace agreement" that sees Israel hold on to the large settlement blocs in the West Bank and maintain security control over the territory.

He opposes any unilateral moves.

"There's a need for change and an opportunity for change," Gantz told Israel's army radio on Monday.

"Israel needs to choose a direction of unification, connection and hope -- or of extremity."

Gantz has sought to overcome Netanyahu's experience and achievements by allying with two other former military chiefs of staff and ex-finance minister Yair Lapid to form his Blue and White alliance.

Neck-and-neck

Opinion polls have given Netanyahu's Likud and Blue and White a similar number of seats in the 120-seat parliament.

Under those polls, both would fall far short of an outright majority -- with around 30 seats each -- and would need to pull together a coalition.

If polling trends hold, Netanyahu would be best placed to build a coalition thanks to smaller right-wing parties allied to him.

But there have been repeated warnings about opinion polls' unreliability in the past and the fact that many voters had said they were undecided.

Should Netanyahu win, he will be on track to surpass founding father David Ben-Gurion as Israel's longest-serving prime minister later this year.

He has been premier for a total of more than 13 years, entrenching himself so firmly at the top that some have labelled him "King Bibi," using his nickname since childhood.

But if he does triumph, he faces the prospect of becoming the first sitting prime minister to be indicted.

The attorney general has announced he intends to indict Netanyahu for bribery, fraud and breach of trust pending an upcoming hearing.

He is not required to step down if indicted, only if convicted with all appeals exhausted.