"Great victory!" Netanyahu wrote on Twitter.
The results secured Netanyahu's place at the helm of the Likud party ahead of the upcoming national elections on March 2.
"With the help of God and with your help," he told his supporters, "I will lead the Likud for a great victory in the elections and will continue to lead Israel to great achievements."
Israel's Channel 12 TV news reported that initial results showed Netanyahu won a landslide victory with about 70 percent of the votes while his rival, Gideon Saar, won about 30 percent.
Final results are expected on Friday morning, said a spokesman for the Likud.
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