Dimona facility
© Planet LabsIsrael's 'secret' nuclear site near Damona
A secretive nuclear facility at the centre of Israel's undeclared atomic weapons programme is undergoing what appears to be its biggest construction phase in decades, satellite photos analysed by the Associated Press (AP) have revealed.

A dig around the size of a football field and likely several stories deep now sits just meters from the aging reactor at the Shimon Peres Negev Nuclear Research Centre near the city of Dimona.

The facility is already home to decades-old underground laboratories that reprocess the reactor's spent rods to obtain weapons-grade plutonium for Israel's nuclear bomb programme, the Israeli newspaper Haaretz reported on Thursday.

What the construction is for, however, remains unclear. The Israeli government did not respond to detailed questions from AP about the work.

Israel neither confirms nor denies having atomic weapons and is among just four countries that have never joined the nuclear Non-Proliferation Treaty, a landmark international accord designed to stop the spread of nuclear arms.

The construction comes as Israel continues its scathing criticism of Iran's nuclear programme, which remains under the watch of United Nations inspectors, unlike its own.

'Significant new construction'

Israel began secretly building the nuclear site with French assistance in the late 1950s in empty desert near Dimona, a city around 90km south of Jerusalem.

It hid the military purpose of the site for years from the United States, even referring to it as a textile factory, Haaretz said.

For several decades, the Dimona facility's layout has remained the same.

However, last week the International Panel on Fissile Materials at Princeton University noted it had seen "significant new construction" at the site via commercially available satellite photos, though few details could be made out.

In the 1960s, Israel used its claims about Egypt's missile and nuclear efforts to divert attention from its work at Dimona - and may choose to do the same with Iran now, Haaretz said.

Jeffrey Lewis, a professor teaching nonproliferation issues at the Middlebury Institute of International Studies at Monterey, told the Israeli newspaper:
"If you're Israel and you are going to have to undertake a major construction project at Dimona that will draw attention, that's probably the time that you would scream the most about the Iranians."