The surprise and unprecedented multifront attack – by air, land and sea – by the Hamas militant group in southern Israel from the Gaza Strip is a result of a "colossal failure" of the country's intelligence agencies, according to media reports and experts.

Militants from Hamas, which rules the Gaza Strip, fired more than 3,000 rockets from the Gaza Strip into Israel on Saturday morning, according to the Israeli military, while Hamas fighters entered southern Israel by land, sea and air, using paragliders and even captured several Israeli soldiers near the border.

At least 350 Israelis, including soldiers, have been killed and more than 1,900 injured in Israel - the deadliest day for the country in at least 50 years. On the Gaza Strip side, there are nearly 300 deaths and about 1,500 wounded in Israel’s counterattack, media reports said on Sunday.

Israel has always prided itself on its intelligence agencies, Shin Bet, the domestic unit, and especially on Mossad, its external spy agency. However, more than 5,000 rockets were fired as dozens of Hamas fighters infiltrated the heavily fortified border in several locations by air, land and sea, catching the country off guard on Sukkot, a major Jewish holiday.

All this happened despite Israel having one of the strongest militaries in the region, security cameras at the fortified border, personnel from both Shin Bet and Mossad in the field, state-of-the-art thermal imaging/motion sensors and even sophisticated border fencing.

Some experts feel that Israel got so totally engrossed in countering Iran and in efforts to foil the Islamic Republic's nuclear programme that it has neglected its own backyard.

Israeli ministers said the military must provide answers about the failure of its intelligence, in a security cabinet meeting held late on Saturday, YNetNews, a leading portal, said.

Ministers criticised Chief of Staff Herzi Halevi claiming he did not find the time to brief them on Saturday. “Some wondered if he had wanted to avoid their difficult questions about the failure of the military intelligence to detect the Hamas plan," the news portal said.

"Every Israeli citizen wants to know how this failure was possible?" Science and Technology Minister Ofir Akunis said. "Why are the Chief of Staff and Intelligence chief not here now? We need more information." He suggested briefings be provided to the ministers three times a day.

A report in Jerusalem Post, a leading newspaper, said, “Gaza was on the back burner in terms of a sense of security threats because Iran-backed proxies have been increasing threats elsewhere” and gave details of the events unfolded over the last three-four years in the region which, it said, led to “Hamas in Gaza appeared isolated, unable to even get more funds from the usual sources, such as Qatar.” “With Israeli normalisation agreements growing in the region, Hamas seemed to present an outdated ideology of living in the past. This seems to have lulled people into a false sense of security,” it pointed out.

Against the repeated warnings following every escalation that a truce would only help Hamas and other Islamic organisations to rebuild their strength for the next round, Israel had agreed to a ceasefire with Hamas recently, which, some experts said, warnings ignored because of domestic constraints of politics.

"Even as Israel’s political chiefs began to convene in emergency consultations, with the full extent of the infiltration and its consequences still unfolding, Hebrew media began quoting unnamed officials castigating the political and military echelons for the fact that Israel, preoccupied with internal argument, had again been taken by surprise,” said a report in Times of Israel.

"The IDF’s assumption, in recent years, was that Hamas was deterred from carrying out major attacks in Israel — fearing the potency of Israel’s response, and wary of plunging Gaza into renewed devastation,” it said, pointing: “All too evidently, that assumption was unfounded.” Eli Maron, the former head of the Israeli Navy told a new channel anchor, “All of Israel is asking itself: Where is the IDF, where is the police, where is the security? It’s a colossal failure; the hierarchies have simply failed, with vast consequences.” The Times of Israel also quoted Amos Yadlin, a former IDF intelligence chief, as saying, (the attack) invoked echoes of the Yom Kippur War — another attack marked by “intelligence failure,” with the enemy initiating conflict.

For scores of Israelis, Saturday’s deadly infiltration immediately revived painful memories of the October 1973 war practically 50 years to the day, in which Israel’s enemies had launched a surprise attack on Yom Kippur, the holiest day in Judaism.

"It cannot be understated or put in less severe terms: The IDF, the strongest military in the Middle East and one of the most respected worldwide, was caught completely by surprise in the Hamas attack on Israel on Saturday,” YNetNews reported.

The British Broadcasting Corporation (BBC), in an analysis, pointed out: “With the combined efforts of Shin Bet, Israeli domestic intelligence, Mossad, its external spy agency and all the assets of the Israel Defence Forces, it is frankly astounding that nobody saw this coming.” “Or if they did, they failed to act on it,” it said, listing Israel’s capabilities ranging from informants’ network, drone attack strikes, and precision assassinations among others, and then added, “To prepare for and carry out such a coordinated, complex attack involving the stockpiling and firing of thousands of rockets, right under the noses of the Israelis, must have taken extraordinary levels of operational security by Hamas.” Some experts are also blaming it on the internal divide within Israel in view of the judicial overhaul plan initiated by the government that has led to massive calls for boycott, depleting strength in positions.

CNN’s intelligence and counter-terrorism analyst Kimberly Dozier weighed in on Hamas strategy and how Israeli intelligence apparently missed the signals of an attack as she said, “How did such a large group of people plan such a large operation without detection by the Israeli side when Israeli defence officials practically bragged about how they infiltrated all Palestini communications in Gaza and the West Bank even if they were using encrypted Apps.” "This is an incredible message on the part of the Palestinians and Hamas that they were able to gather all these weapons and (carry out) multiple massive attacks,” she said.

The Israeli government authorities did seem concerned about Israeli preparedness in a war-like situation and went around checking shelter houses across the country, but it is not clear if that was directed towards a possible fight with Iran or a probable Palestinian attack.

Except for the headline, this story has not been edited by The Telegraph Online staff and has been published from a syndicated feed.