At least nine people were killed and thousands more were injured after a number of handheld pagers exploded across Lebanon on Tuesday, the country's Health Ministry said.
Lebanese Health Minister Firas Abiad said the blasts "killed nine people, including a girl."
"About 2,750 people were injured... more than 200 of them critically," he added.
Hezbollah, a political organization and militant group in Lebanon, said at least two of its members were killed.
More than a dozen others were wounded in Syria, according to the UK-based Syrian Observatory for Human Rights.
"Fourteen people whose nationalities are unknown have been wounded in Damascus and its countryside after pagers used by Hezbollah exploded," the organization said.
Lebanon's Foreign Ministry condemned what it described as a "dangerous and deliberate Israeli escalation." Israel did not immediately comment on the incident.
The Foreign Ministry accused Israel of threatening to "expand the war towards Lebanon on a large scale."
Hezbollah vows 'just punishment' for explosions
Iranian-backed Hezbollah also blamed Israel for the explosions.
"We hold the Israeli enemy fully responsible for this criminal aggression," Hezbollah said.
It added that Israel "will certainly receive its just punishment for this sinful aggression."
A Hezbollah official, speaking on the condition of anonymity, told the Reuters news agency that the incident was "the biggest security breach" the group had been subjected to in nearly a year of conflict with Israel.
Reports that Israel targeted the communications devices and was behind the detonations remain unconfirmed.
There have been near-daily cross-border exchanges between Israel and Hezbollah fighters since Hamas attacked southern Israel on October 7, triggering war in the Gaza Strip.
What we know about the incident
A Hezbollah official, speaking to Associated Press on condition of anonymity because he was not authorized to speak to the media, said the explosions were the result of "a security operation that targeted the devices."
"The enemy [Israel] stands behind this security incident," the official said, without elaborating. He added that the new pagers that Hezbollah members were carrying had lithium batteries that apparently exploded.
BREAKING: Massive explosion hits Hezbollah stronghold in Lebanon! Hundreds of members injured, many seriously, after pagers detonate. Officials call it "biggest security breach" in a year. Chaos ensues with 30-minute prolonged blasts. #Hezbollah#Lebanon#Explosionpic.twitter.com/k53wmmkz4o
According to the German DPA news agency, the Bahman hospital in Beirut received more than 100 people. Some were said to be in critical condition.
The Lebanese Health Ministry urged all hospitals across the country to be on alert. It also advised people to stay clear of devices that might pose a threat.
"The Ministry requests all citizens who own wireless communications devices to stay away from them until the truth of what is happening is revealed," the ministry said in a statement.
Iran's Mehr news agency reported that the Iranian ambassador to Lebanon, Mojtaba Amani, was among those injured.
Hezbollah is considered a terrorist organization by the US, Germany and several Sunni Arab countries, while the EU lists its armed wing as a terrorist group. It also operates as a major political party within Lebanon.
Why is Hezbollah using pagers?
A pager is a wireless telecommunications device that receives and displays messages. It was among the first compact mobile communication devices to reach the mass market, and although smartphones have largely supplanted it, some people still use this technology today.
The pagers use their own frequency and are therefore considered more reliable because they bypass cellular networks, which can experience interruptions, connection problems or interception of communications.
Makram Rabah, a lecturer in the history department at the American University of Beirut, told DW that he believes Hezbollah has purchased a large number of pagers because its landline network and even mobile phone operators have recently been hacked by Israel, which has driven them to a more low-tech fashion.
"By doing so they have been exposed to a new type of danger. And what happened today is proof of that," he said.
Analysts speculate that a Hezbollah supply chain has been infiltrated to cause the simultaneous explosion of hundreds of Hezbollah pagers. A source close to Hezbollah told the AFP news agency that "the pagers that exploded concern a shipment recently imported by Hezbollah of 1,000 devices," which appear to have been "sabotaged at source."
Meanwhile, Taiwan-based company Gold Apollo said it did not make the pagers involved in the blasts.
This comes after a New York Times report suggested the pagers had been supplied by Gold Apollo and shipped to Lebanese militant group Hezbollah.
How did others react?
The United States said it had no knowledge about the incident in advance.
"I can tell you that the US was not involved in it, the US was not aware of this incident in advance and, at this point, we're gathering information," State Department spokesperson Matthew Miller told reporters.
The blasts came after weeks of private diplomacy by the US to prevent an Iranian retaliation against the killing of Hamas political chief Ismail Haniyeh in Tehran in July, which Iran blames on Israel.
"We would urge Iran not to take advantage of any incident to try to add further instability and to further increase tensions in the region," Miller told reporters.
United Nations spokesperson Stephane Dujarric said the developments in Lebanon were concerning, especially given the "extremely volatile" context."
"I think we cannot under underscore enough the risks of escalation in Lebanon and in the region," Dujarric added.
Meanwhile, militant group Hamas — which Israel is fighting in the Gaza Strip and which counts Hezbollah as a key international backer — blamed Israel for the explosions.
"We... strongly condemn the Zionist terrorist aggression that targeted Lebanese citizens by detonating communication devices in various areas of Lebanese territory," Hamas said in a statement.
The organization also said the explosions did not distinguish "between resistance fighters and civilians."
Hamas is designated as a terror group by the US, the EU, Germany and others.
