Votes are being counted following early national elections in Israel on March 17.
Exit polls show a tight race between Prime Minister Benjamin Netanyahu's Likud party and Isaac Herzog's Zionist Union.
Channel 10 and Channel 1 said Likud and the Zionist Union had secured 27 seats each in the 120-member Knesset, while Channel 2 said that Netanyahu had eked out a narrow victory, winning 28 seats to 27 for Herzog.
On Twitter, Netanyahu claimed a "great victory."
Herzog said "everything is open."
Final results are not expected until early on March 18.
Netanyahu is seeking a fourth term.
He campaigned on security issues, promising not to allow a Palestinian state if elected, and warning against any nuclear deal with Iran.
Herzog accused Netanyahu of using scare tactics and ignoring more pressing issues, such as the high cost of living in Israel.
"Against all odds: a great victory for Likud," Netanyahu told cheering supporters in a speech at party election headquarters in Tel Aviv.
He said he had spoken to leaders of other right-wing parties and urged them to form a "strong and stable" government with him without delay.
The exit polls gave right-wing and religious parties - Netanyahu's traditional partners - about 54 seats, and left-leaning factions, 43 - both figures still short of a governing majority in the 120 seat parliament.
Netanyahu on election day accused left-wing groups of trying to remove him from power by busing Arab Israeli voters to polling stations, a statement that drew a sharp rebuke from Washington.
"We're always concerned, broadly speaking, about any statements that may be aimed at marginalising certain communities," State Department spokeswoman Jen Psaki said.
Some political rivals accused Netanyahu of racism over the remarks.
The Obama administration has bee at odds with Netanyahu since he addressed the U.S. Congress two weeks ago at the invitation of Republican lawmakers, to oppose ongoing U.S. nuclear negotiations with Iran.
