Israel is accused of carrying out an audacious, high-tech and targeted attack on Hezbollah.
The unprecedented mass explosion of handheld pagers used by Hezbollah fighters came after the military group switched from mobile phones as a means of communication to reduce the risk of being tracked by Israel.
No one has claimed responsibility but Lebanese officials have accused Israel.
Israel’s security services have a long history of inventive methods to eliminate their enemies.
Pager explosions: Middle East latest
How pagers could be deployed as bombs
A security expert, speaking on condition of anonymity, has described how someone could have tampered with these devices before they were distributed – such as by hiding explosives inside them that could be detonated remotely when a certain signal is sent to the pager.
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The source said the “general view I am hearing is that this was an impressive attack” which required a certain amount of co-ordination.
“It looks likely that the pagers they [Hezbollah] purchased may have been compromised and turned into remote bombs,” the security expert said, stressing that this was just speculation based on his expertise.
“[It] seems too coordinated and powerful an explosion to just be malfunction,” adding it was less likely to have been caused by the batteries overheating.
Israel’s long history of high-tech warfare
Israel’s spy agencies have a long history of being linked to assassinations and covert activities using high-tech bombs and devices. Here is a summary of some of them:
1972: Bassam Abu Sharif
He was injured in Beirut when he opened a package containing a book implanted with a bomb which exploded. He was the spokesperson for the Popular Front for the Liberation of Palestine (PFLP).
He survived but lost several fingers, was left deaf in one ear and blind in one eye.
1972: Mahmoud Hamshari
A representative from the Palestine Liberation Organisation (PLO) was killed in Paris in 1972 when a bomb was planted under a telephone and remotely detonated.
1996: Yahya Ayyash
The Hamas bombmaker was killed when he was given a mobile phone that had been bugged and contained explosives which were detonated remotely.
He earned the nickname “The Engineer” and apparently helped develop suicide bombs used in the Israeli-Palestinian conflict.
2000: Samih Malabi
A Fatah activist from the Kalandia refugee camp outside Ramallah, was killed when a booby-trapped mobile phone exploded next to his head.
2007: Stuxnet
A powerful computer worm designed by US and Israeli intelligence that is believed to have disabled a key part of the Iranian nuclear program.
Stuxnet was designed to destroy the centrifuges Iran was using to enrich uranium as part of its weapons programme.
It is reported the worm was delivered to the facility on a thumb drive by an Iranian double agent working for Israel.
2020: Mohsen Fakhrizadeh
An Iranian nuclear scientist was assassinated in Iran by a remote-controlled machine gun mounted on a car.
Mr Fakhrizadeh was travelling in a bulletproof vehicle alongside three security personnel vehicles when he heard what sounded like bullets hitting his car.
After he reportedly left the vehicle, a Nissan fitted with a remote-controlled machine gun then opened fire killing him.