While Israel has never admitted to having nuclear weapons, few international experts question the Jewish state's presence on the world's list of nuclear powers.
Israel built the Dimona plant with help from France
Its nuclear capability is arguably the most secretive weapons of mass destruction programme in the world.
Unlike Iran and North Korea - two countries whose alleged nuclear ambitions have recently come to the fore - Israel has never signed the Nuclear Non-Proliferation Treaty, designed to prevent the global spread of nuclear weapons.
As a result, it is not subject to inspections and the threat of sanctions by the United Nations nuclear watchdog, the International Atomic Energy Agency.
The extent of Israel's nuclear capability has been the subject of often wildly inaccurate intelligence estimates since the 1960s, when the country's nuclear reactor, at Dimona in the Negev desert, came online.
The shrouds of secrecy have lifted only once, in the mid-1980s, when a former worker at the plant, Mordechai Vanunu, gave a British newspaper descriptions and photographs of Israeli nuclear warheads.
Vanunu's evidence led to a sharp upwards revision of the number of nuclear warheads Israel was believed to possess - to at least 100 - and possibly as many as 200.
By way of comparison, India and Pakistan - the most recent members of the "nuclear club" - are widely believed to have about 20 warheads each. They successfully carried out nuclear weapons tests in 1998, leading to fears of an escalated conflict between the two rival South Asian powers.
There is no evidence that Israel has ever carried out a nuclear test, but there is speculation that a suspected nuclear explosion in the southern Indian Ocean in 1979 was a joint Israeli-South African test. Post-apartheid South Africa has dismantled its nuclear weapons programme.
Shortly after its creation as a Jewish homeland in 1948 and following the horrors of the Holocaust, in which six million European Jews were murdered, Israel began showing an interest in acquiring nuclear weapons - the "ultimate deterrent".
In 1952, the Israeli Atomic Energy Commission was formed and began working closely with the Israeli military.
By 1953, a process for extracting uranium found in the Negev desert was perfected and a new method of producing heavy water was developed - providing Israel with its own capability to produce some of the most important nuclear materials.
For reactor design and construction, Israel sought and received the assistance of France.
Mordechai Vanunu: Viewed as a traitor and a spy by most Israelis
According to Washington-based website GlobalSecurity.org, a secret agreement between the two nations saw construction of the Dimona plant begin in the late 1950s.
The complex was variously described as a textile plant, an agricultural station and a metallurgical research facility until 1960, when Prime Minister David Ben-Gurion stated that it was a nuclear research centre built for "peaceful purposes".
From its early suspicions that Israel had nuclear ambitions - overflights by U-2 spy planes revealed Dimona's construction in 1958 - the United States expressed concern.
During the 1960s, US inspectors visited Dimona several times but were unable to obtain an accurate picture of the activities carried out there.
GlobalSecurity.org says the Israelis went so far as to install false control room panels and to brick over elevators and hallways that accessed certain areas of the facility.
The inspectors were able to report that there was no clear scientific research or civilian nuclear power programme justifying such a large reactor - seen as circumstantial evidence of the Israeli bomb programme - but found no evidence of "weapons-related activities".
In 1968, a US Central Intelligence Agency report concluded that Israel had begun to produce nuclear weapons.
Years of speculation about the size of Israel's nuclear arsenal followed.
The Vanunu affair
In 1986, Mordechai Vanunu, who had worked as a technician at the Dimona complex, gave London's Sunday Times newspaper detailed information about Israel's nuclear programme that led observers to declare Israel the world's sixth largest nuclear power.
Before he could reveal more to the media, Vanunu became the victim of a classic "honey trap".
He was lured out of hiding in London by a female Israeli secret agent who persuaded him that she wanted to meet him in Rome. Once there, he was drugged by other Israeli agents and brought home.
Later that year, he was jailed for 18 years after a trial for treason that was held in secret. Viewed as a traitor and a spy by most Israelis, Vanunu remains in prison to this day and has spent most of his sentence in solitary confinement.
Israel's former Prime Minister Shimon Peres, widely regarded as the architect of Israel's nuclear weapons programme, testified at the trial that Vanunu had done serious damage to Israel's security.
Mr Peres subsequently said: "A certain amount of secrecy must be maintained in some fields. The suspicion and fog surrounding this question are constructive, because they strengthen our deterrent."
Other states in the Middle East, many of them strong supporters of the Palestinian cause, have expressed deep concern about the existence of an Israeli nuclear weapons programme.
They also accuse the US of operating a regional policy of double-standards, ignoring Israel's weapons programmes while insisting that others - notably pre-war Iraq, Iran and Syria - are a threat to peace because of their alleged weapons of mass destruction.
The head of the International Atomic Energy Agency recently urged Israel to sign the Nuclear Non-Proliferation Treaty and surrender its nuclear weapons in order to further peace in the Middle East.
The head of the IAEA, an Egyptian, is regarded with suspicion in Israel
Mohamed ElBaradei told an Israeli newspaper, Haaretz, that the IAEA operated under the assumption that Israel had nuclear weapons despite the fact that it had never officially confirmed this.
He warned that Israel's belief that it was safer because it possessed such weapons was false, as other Middle Eastern countries felt threatened by their presence.
And he urged Israel and its neighbours to begin talks on halting the spread of nuclear weapons in the Middle East.
"My fear is that, without such a dialogue, there will be continued incentive for the region's countries to develop weapons of mass destruction to match the Israeli arsenal," he said.