Covert and lethal Unpicking the global trail behind compromised kit

It may be years before the full story is told of how a coordinated explosion of thousands of pagers and walkie-talkies used by Hezbollah was orchestrated.

- Dan Sabbagh, Lili Bayer, Dan Milmo

But, even without Israel publicly admitting responsibility, it is clear that the attack was carefully planned - however uncertain its consequences.

Experts generally believe a small mount of stable explosive was carefully implanted into each sabotaged device. Alan Woodward, a professor of cybersecurity at Surrey University, said: "There wouldn't need to be much explosive as proximity to a human body means it would cause injury even if it was a few grams." The first wave of explosions from about 3.30pm on Tuesday - appear to be have been triggered by a special message, appearing to be from Hezbollah leadership, implying, Woodward said, a specific modification of the pagers' embedded software. This meant it would trigger an explosion whenever the message was sent.

It may have been a default setting of the pagers, but the trigger message came with a cynical twist.

Witnesses say the pagers bleeped, then paused, then detonated enough time to bring them closer to the owner's face - which is why doctors reported treating multiple hand and eye injuries.

Twelve people were killed and about 2,800 injured in Tuesday's explosions, and 14 died in a second wave that followed yesterday when walkie-talkies starting blowing up.

This suggests the attacks amounted to a concerted attempt to disrupt Hezbollah's communications - the kind of activity that could be a prelude to a bombing raid of south.

Lebanon or other conventional military attack.