Hezbollah’s pagers were meant to be safety measures, secure from Israeli eavesdropping.

Instead, they were a deadly Trojan horse.

After suffering a series of assassinations of top operatives during months of low-level war with Israel, this summer Hezbollah ordered its fighters to ditch their mobile phones. They were too easy to track and too readily compromised by Israel’s fearsome military hackers.

“If you’re looking for an Israeli agent, look at the phone in your hand,” Hassan Nasrallah, Hezbollah’s chief, warned his men.

Instead, communications would be confined to more old-fashioned means: couriers delivering messages by word of mouth.

Telecoms would be limited to 1980s-style pagers, with none of the vulnerabilities of smartphones, Hezbollah sources told Reuters in July.

Thousands of the latest and most secure models were duly procured and distributed to top fighters, officials and allies.

On Tuesday afternoon, that was revealed as a terrible blunder.

At 3.45pm local time, thousands of pagers in thousands of pockets simultaneously exploded.

By early evening at least nine people had been confirmed killed and a staggering 2,750 injured.

Firass Abiad, Lebanon’s health minister, said 200 of them were in a critical condition.

The wounded reportedly included civilians as well as Hezbollah fighters and even Iran’s ambassador to Lebanon, although the reports could not immediately be verified.

In one greengrocer’s a middle-aged man had reached the grape counter when a puff of smoke leapt from his midriff.

He fell, screaming to the floor, badly wounded by the explosion from his pocket, bag or belt. The young man serving him leapt instinctively away.

The nearest bystander, after understandably making sure he himself was unhurt, simply stood over the screaming man, as he writhed on the floor, at a loss as to what to do.

They were not alone in being nonplussed.

Ahmad Ayoud, a butcher from the Basta neighbourhood in Beirut, told the New York Times he was in his shop when he heard explosions and saw a man in his 20s fall off a motorbike.

“We all thought he got wounded from a random shooting,” Ayoud said. “Then, a few minutes later, we started hearing of other cases. All were carrying pagers.”

Within minutes, ambulances were rushing through Beirut.

Many of the wounded, screaming in pain, were rushed to hospital on motorbikes. Doctors reported patients with bloodied hands, faces, and eyes.

Iran’s Fars news agency said Mojtaba Amani, the Iranian ambassador in Beirut, had suffered superficial injuries and was under observation in hospital.

Ziad Makary, Lebanon’s information minister, said the government condemned the detonation of the pagers as an “Israeli aggression”.

Hezbollah blamed Israel for the pager blasts and said it would receive “its fair punishment”.

Israeli officials declined to comment.

One Hezbollah official, speaking to Reuters, described it as the “biggest security breach” the group had suffered in a year of conflict with Israel.

That does not appear to be hyperbole. The questions remain about the mechanism of the attack.

Lebanese internal security forces said a number of wireless communication devices were detonated across the country, especially in Beirut’s southern suburbs, a Hezbollah stronghold.

In today’s tech-obsessed world, the idea of some kind of mass cyber attack causing the pagers’ batteries to overheat or malfunction in some way sounds believable.

It would fit with the current dystopian zeitgeist to learn that our mobile devices are not only destroying our attention spans but could also be turned into bombs.

Fortunately, from the point of view of ordinary pager and electronics users – not to mention their manufacturers – that does not seem to be what happened.

Alan Woodward, a cyber security expert at the university of Surrey, said: “I’ve heard of Lithium ion batteries spontaneously igniting but to make it happen on demand is a different matter entirely.”

“Lithium battery fires and explosions are a general problem but this looks a bit more than this,” agreed Hamish de Bretton Gordon, a retired British army chemical weapons expert.

“There must be some sort of ‘accelerant’ to make them combust in such a violent fashion – probably some form of high explosive, possibly 10 grams of HMX.”

HMX, also known as octogen, is a widely used military explosive. Mr Woodward guessed the attack might have used C4, another common military explosive.

That would imply a “supply chain attack” in which the perpetrators – and although they are not commenting, that almost certainly means the Israeli security services – had physical access to the devices to embed the explosive.

The impacted devices appeared to have included “rugged” pagers developed by Taiwanese company Gold Apollo, according to reporters at Bellingcat.

Explosive timer

Security sources told Reuters that the devices had been procured in recent months.

The charge could be set to trigger on receipt of a particular message or even simply timed to explode with an old-fashioned timer, said Mr Woodward.

Ken Munro, founder of cyber security company Ken Test Partners, said: “I’m leaning hard towards a supply chain attack, as to remotely cause a battery to explode in such a fashion would be extremely challenging.”

Intriguingly, the attack came just hours after Israel’s domestic security agency said it had foiled a similar – though much smaller scale – plot by Hezbollah.

The Shin Bet said in a statement it had seized an explosive device attached to a remote detonation system, using a mobile phone and a camera that Hezbollah had planned to use to kill a former Israeli military official in Tel Aviv.

It said the group had planned to operate the device remotely from Lebanon.

The attack comes a day after Israel’s defence minister said the country would take military action to return civilians to the north of the country, stoking fears of an all-out Israel-Hezbollah war.

It follows nearly a year of low-level but intensifying conflict, and came a day after the Israeli government made returning evacuated 60,000 civilians to their homes in the north of the country an official war goal.

The fighting began when Hezbollah launched strikes following Israel’s attack on Hamas in Gaza in response to the October 7 terrorist attacks.

The conflict has mostly been concentrated along the Lebanon-Israel border.

But it has also seen Israeli airstrikes across Lebanon and Hezbollah rocket strikes deep into Israel.

Although so far both sides have shied away from attacks on a scale likely to spark a full-scale war, thousands of civilians have fled from both sides of the frontier.

Yoav Gallant, the Israeli defence minister, told Amos Hochstein, a visiting US envoy, this week that the window for a negotiated end to the fighting with Hezbollah was closing.

It meant that “the only way left to ensure the return of Israel’s northern communities to their homes will be via military action”.