In September 1986, Mordechai Vanunu, a technician at Israel's Dimona nuclear site, revealed to the Sunday Times that the nuclear military programme based there had produced 'over 200' nuclear warheads.

Days later he was tricked into flying to Rome where he was abducted by Mossad agents and secretly transported to Israel. In November 1986, he was tried in camera and sentenced to 18 years' imprisonment, 14 of which were spent in solitary confinement.

In 1999, in response to a petition from Yediot Ahronot newspaper, the government released about 40 per cent of the trial documents.

The Bulletin of the Atomic Scientists estimates that Israel has the world's fifth largest stockpile of nuclear warheads (more than Britain, which it believes has 185).

In February 2000, Knesset member Issam Mahoul said Israel had '200 to 300' nuclear weapons; in August of that year, the Federation of American Scientists said that Israel could have produced 'at least 100 nuclear weapons, but probably not significantly more than 200'; the Stockholm International Peace Research Institute estimates 200.

Other sources, including Jane's Intelligence Review, estimate between 400 and 500 thermonuclear and nuclear weapons.

What Dimona is to Israel's nuclear programme, the Israeli Institute for Biological Research (IIBR) at Nes Ziona is to its chemical and biological warfare (CBW) programme. The high-security facility is absent from aerial survey photographs and maps, on which it has been replaced by orange groves.

Except for token visits to Dimona by a Norwegian team in 1961 and a US team in 1969, there has been no international scrutiny. Even the Knesset is denied access.

However, the 1993 report by the Office of Technology Assessment for the US Congress states that Israel has 'undeclared offensive chemical warfare capabilities' and is 'generally reported as having an undeclared offensive biological warfare programme'.

Anthony Cordesman of the Centre for Strategic and International Studies states that Israel has conducted extensive research into gas warfare and is ready to produce biological weapons.

According to an exhaustive study by Karel Knip, a Dutch journalist, the IIBR's work has included the synthesis of nerve gases such as tabun, sarin and VX.

The October 1992 crash an of El Al cargo plane in Amsterdam that caused at least 47 deaths and caused hundreds of immediate and subsequent mysterious illnesses led to the disclosure in 1998 that flight LY1862 was carrying chemicals including 50 gallons of dimethyl methylphosphonate (DMMP) - enough to produce 594 pounds of sarin. The DMMP was supplied by Solkatronic Chemicals Inc of Morrisville, Pennsylvania, and was destined for the IIBR.

Avner Cohen has catalogued reported uses of biological weapons by Jewish forces during the 1948 war in Palestine. The Israeli historian Uri Milstein alleged that 'in many conquered Arab villages, the water supply was poisoned to prevent the inhabitants from coming back.' Milstein states that one of the largest of such covert operations caused the typhoid outbreak in Acre in May 1948.

The Palestinian Arab Higher Committee reported in July 1948 that there was some evidence that Jewish forces were responsible for a cholera outbreak in Egypt in November 1947 and in Syrian villages near the Palestinian-Syrian border in February 1948.

In May 1948, the Egyptian ministry of defence stated that four 'zionists' had been captured while trying to contaminate artesian wells in Gaza with 'a liquid which was discovered to contain germs of dysentery and typhoid'.

In 1954, it was widely reported that defence minister Pinchas Lavon had proposed using BW for special operations. Cohen says: 'Israel has presumably employed biological or toxin weapons for special operations.'

In 1955, Prime Minister Ben Gurion ordered the weaponisation and stockpiling of chemical weapons in case of a war with Egypt. Former Mossad agent Victor Ostrovsky claims that lethal tests have been performed on Arab prisoners at the IIBR.

There are allegations that Israel has used CBW on numerous occasions:

 Chemical defoliants used by the army against Palestinian lands, including Ain el-Beida in 1968, Araqba in 1972 and Mejdel Beni Fadil in 1978;
 Armed nuclear missiles in the 1967 and 1973 Arab-Israeli wars;
 Chemical weapons in the 1982 war on Lebanon, including hydrogen cyanide, nerve gas and phosphorus shells;
 In the 1980s lethal gases against Palestinian civilians and Palestinian, Lebanese and Israeli Jewish prisoners.

Discussing delivery systems, the Bulletin of Atomic Scientists states that Israel's F-16 squadrons based at Nevatim and Ramon are the most likely carriers of nuclear warheads and that a small group of pilots has been trained for nuclear strikes.

According to the Sunday Times, F-16s crews are also 'trained to fit an active chemical or biological weapon within minutes of receiving the command to attack'. Israel's F-4s, F-15s and Jaguars are also nuclear-capable.

Israel's Jericho I (with a range of 660km) and Jericho II (1,500km) missiles are nuclear-capable. The Shavit satellite launch vehicle is convertible into an intercontinental ballistic missile with a range of 7,800km.

Israel also has three Dolphin-class submarines, the Dolphin, the Leviathan and the Tekuma, which are reportedly modified to carry nuclear-tipped cruise missiles.

It is widely believed to possess a tactical nuclear capability, including small nuclear landmines, and strategic nuclear warheads that it can fire from cannons.

The UN Security Council regularly calls on Israel 'urgently to place its nuclear facilities under the safeguards of the International Atomic Energy Agency.'

Israel has signed but not ratified the Chemical Weapons Convention, but is one of only four countries in the world - with Cuba, India and Pakistan - not to have signed the Nuclear Non-Proliferation Treaty .