Thousands of people in Lebanon and Syria have been wounded and at least eight killed in an initial toll when pagers belonging to Hezbollah personnel and other individuals exploded on Tuesday, in a massive and unprecedented security breach blamed on Israel.
The Iran-backed Shia group has been engaged in nearly year-long cross-border fire with Israel since the war on the Gaza Strip began last October.
Hezbollah has blamed Israel for Tuesday's attack, which comes at a time of once again rising tensions between both sides.
So, what do we know so far?
What happened?
At around 3.30 pm local time (1230pm GMT), pager devices being carried by Hezbollah-affiliated personnel and other Lebanese civilians began to detonate.
Ambulances began rushing to collect the wounded, and hospitals in the southern suburbs of Beirut, south Lebanon, the Beqaa region, as well as in Syria – where Hezbollah still maintains a presence since the war there started – soon after became flooded, with calls to donate blood.
The causes behind the detonations remain unknown, but rumours have begun to spread like wildfire.
While some have speculated that Israel had somehow managed to hack the devices and blow them up, others have said the explosion could have been due to a smaller device fitted into the pagers.
Preliminary reports say the pagers' batteries had exploded.
Some sources have said the pagers were the latest model brought in by Hezbollah in recent months.
Mass casualties
Lebanon’s health ministry has confirmed 2,800 injuries – "more than 200 of them critically" – and eight killed.
Among the fatalities is the 10-year-old daughter of a Hezbollah member, who died after a pager that was next to her blew up in the village of Sar’in in the Baalbek district.
The son of Hezbollah MP Ali Ammar was also confirmed dead.
Iran’s ambassador to Beirut, Mojtaba Amani, was confirmed wounded, but his injuries were not serious, Lebanese state media reported.
A senior source from Hezbollah denied that the group’s leader, Hassan Nasrallah, was hurt in a blast.
Hezbollah promises to punish Israel
The strange incident has rocked Lebanon and the powerful militant group.
In an initial statement, Hezbollah said it was investigating the cause behind the explosions.
It called on people to be aware of "rumours and false and misleading information" that could serve the "psychological warfare" conducted by the "Zionist enemy," in light of Israel’s threats to invade southern Lebanon.
In a second statement, the group openly blamed Israel.
"After examining all the facts, current data, and available information about the sinful attack that took place this afternoon, we hold the Israeli enemy fully responsible, and this treacherous and criminal enemy will certainly receive its just retribution for this sinful aggression," the statement read.
Has Israel said anything?
The Israeli government has not yet commented on the incident.
Reports in Israeli media said Israel’s Prime Minister Benjamin Netanyahu, Defence Minister Yoav Gallant and other security chiefs gathered at a defence ministry headquarters at a military base in Tel Aviv to discuss possible escalation with Hezbollah following Tuesday’s bloody event.
Israeli media also reported that the military’s ‘Home Front Command’ has also warned local authorities of a possible escalation, but that there was no "current change" to civilian guidelines.
It remains unclear how Hezbollah intends to respond, or if it does.
At the end of July, Israel killed the Iran-backed militant group’s number two in an airstrike on a southern suburb of Beirut, where hundreds on Tuesday were injured in the pager explosions.
Hezbollah responded to that assassination in August.