Israel's embattled Prime Minister Benjamin Netanyahu has won a leadership primary in his right-wing Likud party, ensuring he will lead it into March elections.

Israel's longest-serving premier, who faces a corruption indictment and a third general election in 12 months, was expected to beat rival Gideon Saar but a close result could have weakened his influence over the party he has dominated for 20 years.

With all votes counted, the Likud announced that Mr Netanyahu had secured 72.5%, with Mr Saar winning 27.5%. 

"A huge win! Thank you to Likud members for their trust, support and love," Mr Netanyahu tweeted an hour after polls closed.

Gideon Saar

"With God's and your help, I will lead Likud to a big victory in the upcoming elections and we will continue to lead the State of Israel to unprecedented achievements," Mr Netanyahu added.

Around 57,000 Likud members cast their ballots across the country, a little less than 50% of those eligible.

Mr Saar, a former minister seen as to the right of Mr Netanyahu, conceded early today.

"I am content with my decision to have stood. Those who are unwilling to take a risk for what they believe in will never succeed," Mr Saar tweeted.

"My colleagues and I will stand behind (Netanyahu) in campaigning for the Likud's success in the general elections," he added.

Mr Saar announced his leadership challenge last month after Israel's attorney general indicted Mr Netanyahu for fraud, bribery and breach of trust.

The 70-year-old denies the allegations.

He will now remain Prime Minister until new elections in March.

Likud and the centrist Blue and White were near neck-and-neck after polls in March and September, with neither able to form a coalition in the country's proportional parliament.

Mr Netanyahu's downfall has been predicted multiple times since he became premier for a second time in 2009, but he has defied expectations and appears determined to fight on.

Mr Netanyahu has consistently accused the police, prosecutors and the media of a witchhunt.

Under Israeli law, a prime minister is only forced to step down once convicted with all appeals exhausted.