Israel’s Channel 1 and Channel 10 exit polls give Netanyahu’s Likud party 27 seats, and Herzog’s Zionist Union party 27 seats in a 120-member Parliament.
Meanwhile, Israel’s Channel 2 exit poll gives Netanyahu’s Likud party 28 seats, and Herzog’s Zionist Union party 27 seats in Parliament.
The Joint List grouping Israel's main Arab parties took third place in Tuesday's general election, winning 13 seats, exit polls showed.
Results published by both Channel 2 and Channel 10 television gave the Joint List 13 seats.
Closely following was the centrist Yesh Atid, which took 12 seats in the first poll and 11 in the second, in figures published within minutes of the close of polling stations.
Final results are not expected until early Wednesday morning, but Israeli political analysts agreed that Netanyahu had the advantage, with more votes having gone to the right-leaning parties likely to support him.
Earlier Tuesday in the midst of the deadlock, Netanyahu, on Twitter, claimed a "great victory.”
"Against all odds: a great victory for Likud, a great victory for the national camp led by Likud, a great victory for the people of Israel," Netanyahu wrote on his official Twitter account.
— בנימין נתניהו (@netanyahu) March 17, 2015
Netanyahu said late Tuesday he'd begun inviting other rightist politicians to join him in forming a coalition government "without delay."
Herzog, on the other hand, is refusing to concede, insisting that the final results are unknown. In his first remarks since exit polls reported a virtual tie with Netanyahu’s Likud party, Herzog told a crowd of his supporters “today we scored an extraordinary achievement.”
“There won’t be any decisions taken tonight," he added. "Everyone can go to sleep. You gave your heart and soul. Thank you.”
The most recent opinion polls had shown a close race heading into the vote, with Netanyahu's opponents, led by Herzog, in a slight lead.
On Tuesday, before the release of exit poll results and amid worry that he could be ousted from office, Netanyahu made a last-ditch effort to rally his supporters, warning that a large turnout by Arab voters could endanger his right-wing party’s political dominance.
"We are in a fateful campaign. The only way to minimize that gap is to go to the polling station and vote" Likud, Netanyahu was quoted as saying by the Associated Press.
During the final stages of the campaign, with increasing chances of his six-year reign coming to an end, Netanyahu complained of an international conspiracy funded by wealthy foreigners to oust him.
The warning about Arab voters came in a message from Netanyahu’s Likud Party.
"Voter turnout in the Arab sector is three times higher! The threat is real: Abu Mazen's calls and American money are getting the Arab vote out. Go and vote."
The message quickly drew accusations of racism. Israel's Arabs, who make up 20 percent of the population, have long complained of discrimination.
Also on Tuesday, the prime minister renewed a pledge to prevent the establishment of a Palestinian state, risking further alienating himself from President Barack Obama, whose administration supports a two-state solution to the Arab-Israeli conflict.
Earlier this month, Netanyahu visited Washington and finally delivered a controversial speech to a joint session of Congress. During the address, which came at the request of Republican House Speaker John Boehner, Netanyahu called for American lawmakers to impose sanctions against Iran’s nuclear program.
From the day Boehner’s invitation to Netanyahu was announced, the impending visit drew criticism from Democratic lawmakers in Washington, and subsequently brought Netanyahu’s already chilled relationship with the Obama administration to an all-time low.
The reaction was similarly divisive in Israel, where some, including the former head of Israel spy agency Mossad, accused Netanyahu of jeopardizing Israel’s historically strong relationship with the United States, and called on voters to remove him from office.