Israel's prime minister says attempts by pro-Palestinian protesters to breach the Israeli frontier show that Israel's very existence is at the center of the Mideast conflict.

Benjamin Netanyahu says the protesters are not interested in a state alongside Israel. "The argument is over the fact of the establishment of the state of Israel," he told reporters.

The border was quiet Monday after Syrian police stopped protesters from reaching the fence.

On Sunday, hundreds of protesters from Syria, most of them Palestinian refugees, surged pasts Syrian checkpoints toward the Israeli line on the Golan Heights, breaching barbed wire and sparking clashes with Israeli soldiers.

A Syrian government official said 23 people were killed. The number could not be independently verified.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

MAJDAL SHAMS, Golan Heights (AP) _ Syrian police blocked dozens of pro-Palestinian protesters from approaching the Israeli frontier on Monday, preventing a repeat of deadly clashes with Israeli forces that killed as many as 23 people who tried to rush the border.

Israeli officials said the instability in Syria ruled out any prospects for peace and accused the government of orchestrating the deadly unrest to deflect attention from its own crackdown on homegrown protests. Israel also questioned Syria's reported death toll.

Syrian police set up a pair of checkpoints on Monday, including one a half-mile (kilometer) from the Israeli-controlled Golan Heights. Nearly 20 protesters, some waving Syrian flags, were walking down a hill leading to the border when two police officers blocked their advance by extending their arms.

Protesters passed Syrian and U.N. outposts without impediment on Sunday and during a similar border rush three weeks ago, and it was not clear why Syrian security forces intervened Monday.

The repeated border challenges play into widespread Israeli fears that the Palestinians will not make do with a state on lands captured in 1967, but want to take over all of historic Palestine, including present-day Israel.

Israeli Defense Minister Ehud Barak suggested that the Syrian regime, which harbors militant Palestinian groups such as Hezbollah and a half-million Palestinian refugees in camps along the border, might have instigated Sunday's unrest _ and similar unrest three weeks ago. He said it was an attempt to deflect the focus from a crackdown on its own protesters. At least 35 Syrians died in a government assault in the country's north over the weekend and Syrian television reported 40 police were killed in an ambush on Monday.

"Could be they think it diverts attention. We have no choice. We have to defend our border," he said.

Barak also challenged the Syrian death toll, saying soldiers had fired only "selectively" at rioters and noting Syria's silence about casualties in its own domestic unrest. He acknowledged there was no way to be sure.

Israeli Foreign Ministry spokesman Yigal Palmor said Israel would file a complaint to the U.N.

Barak also predicted that Syrian President Bashar Assad is irreparably weakened by the uprising. "I think Assad will fall," Barak told Israel Radio on Monday.

Human rights groups say more than 1,200 people have died in the crackdown against anti-government protesters in Syria since March. Assad has coupled military operations with symbolic overtures the opposition has rejected, including an amnesty for many prisoners and a call for national dialogue.

The instability in Syria, Barak said, rules out current peacemaking prospects. Israel and the Syrians last held talks in 2008, but they broke down upon the outbreak of Israel's war in the Gaza Strip.

As its price for peace, Syria demands a return of the Golan, a strategic plateau overlooking northern Israel that Israel captured in 1967 and annexed 14 years later. The annexation is not internationally recognized.

With the frontier calm on Monday, Israeli troops repaired a coil of barbed wire that protesters had cut through on Sunday to enter a trench in a buffer zone that Israel had dug after the violence three weeks ago.

Syrian officials did not explain why they blocked Monday's attempt to cross, but portrayed it as a spontaneous march.

"This was the people's will," said Imad Fawzi Shueibi, a Syrian political analyst with close ties to the regime.

Syrian Health Minister Wael al-Halqi said Monday that 23 people, including a child, were killed and 350 were wounded when soldiers opened fire and blocked them from entering the Golan. A Syrian Foreign Ministry statement issued Monday said the Palestinian and Syrian demonstrators were reaffirming their natural and legal right to liberate and return to their land.

Seven of the dead, their coffins draped with Palestinian flags, were buried Monday at a Palestinian refugee camp outside Damascus. Women on balconies showered the coffins with rice and flowers in a traditional sign of grief.

The other 16 were to be buried later in the day at another camp in the Syrian capital.

British Foreign Secretary William Hague voiced concern about the casualties.

"We recognize Israel's right to defend herself," he said in a statement, but added, "It is vital that any response is proportionate, avoiding lethal use of force unless absolutely necessary, and that the right to protest is respected." He also urged Syria to avoid "provocative acts."

Both Palestinian governments _ the Western-backed Palestinian Authority in the West Bank and the anti-Israel Hamas government in Gaza _ praised the protesters.

Azzam Ahmed, a top aide to Palestinian President Mahmoud Abbas, accused Israel of "brutally" attacking peaceful Palestinians who "have the right to return to their homes and land."

In Gaza, Hamas ordered three days of mourning, calling the dead "martyrs of Palestine."

Israeli opposition lawmaker Binyamin Ben-Eliezer, a former general and defense minister, predicted that unrest would only grow at Israel's various borders.

"There is only one solution," said Ben-Eliezer, whose Labor Party splintered, then quit the government in frustration over its failure to break a stubborn impasse in peacemaking with the Palestinians. "To recognize a Palestinian state and sit down tomorrow at the bargaining table," he told Israel Radio.

Sunday's unrest marked the anniversary of the Arab defeat in the 1967 Middle East war, when Israel captured the Golan Heights from Syria, the West Bank and east Jerusalem from Jordan, and the Gaza Strip and Sinai peninsula from Egypt in six days of fighting.

The recent protests have drawn attention to the plight of Palestinian refugees who fled or were expelled from homes in Israel during the war over Israel's 1948 creation. The original refugees, and their descendants, now number several million, and they demand "the right to return" to the families' former properties.

Israel opposes their repatriation because Palestinians would eventually outnumber Jews in the Jewish state. The fate of the refugees and their descendants is one of the toughest issues in any future Israeli-Palestinian peace accord.

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Aji contributed to this report from Quneitra, Syria.