Reports that sabotaged pagers and walkie-talkies were made by Israeli front company with links to Europe

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A meticulous manufacturing operation, probably controlled by an Israeli front company, is emerging as the most likely way thousands of pagers and walkie-talkies containing hidden explosives ended up in the hands of Hezbollah operatives.

Experts said the sabotaged devices appeared to use small amounts of military grade plastic explosives that could be carefully assembled only over a period of time, amid reports that they were manufactured by an Israeli front company with links to Europe.

Israel is widely believed to be behind the operations – but who made the devices, and how did they explode?

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It may be years before the full story is told of how the coordinated explosions of thousands of pagers and walkie-talkies used by Hezbollah were orchestrated. But, even without Israel publicly admitting responsibility, it is clear that the attack must have been 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.”

Twenty killed and at least 450 injured in cities across Lebanon a day after exploding pagers killed 12

• Analysis: Pager and walkie-talkie attacks were audacious and carefully planned

A new series of extraordinary explosions aimed at Hezbollah – this time targeting walkie-talkies – has killed at least 20 and wounded more than 450 in cities across Lebanon, as international observers warned that the simultaneous detonation of thousands of booby-trapped communications devices may constitute a war crime.

The targeted detonations of the walkie-talkies came one day after more than 2,800 were injured and 12 killed by exploding pagers in an attack blamed on Israel that world leaders and diplomats have warned could lead to an all-out conflict between Israel and the powerful militant group despite efforts by the US and UN to avert an escalation with Hezbollah.

Known for its wineries and Roman temples, and as the home of Hezbollah, the Beqaa has become a theatre of war again

On a recent morning near the town of Nabi Chit in Lebanon’s eastern Beqaa region, a dozen men were clearing away debris. Israeli jets had thundered through the valley a week earlier, the second such raid in three days. The explosions turned the night sky red, yellow and orange, and filled the air with the smell of dust and gunpowder.

“They hit Nabi Chit because our village is the mother of the resistance,” said Mohammed al-Moussawi, an ardent supporter of Hezbollah, the Shia militant group, political party and social movement known here as the resistance. He stood on the ground-floor terrace of his house in front of a pile of rubble and a twisted metal awning. The windows were blown out, the facade pockmarked with shrapnel.