Dozens of members of the Lebanese militant group Hezbollah have been seriously wounded after pagers they use to communicate exploded, security officials say.
A Hezbollah official, speaking on condition of anonymity, told Reuters news agency the detonation of the pagers was the "biggest security breach" the group has faced in nearly a year of war with Israel.
A senior military intelligence official and an official with a Lebanese group also told the AP news agency that pagers carried by Hezbollah members were detonated.
According to AP, a Hezbollah official said that at least 150 people, including members of the group, were wounded in different parts of Lebanon when the devices exploded.
Other reports have cited varying figures of how many are injured.
A statement from the Lebanese prime minister's office said it was informed of "security incidents occurring in a number of regions".
Iran's ambassador to Lebanon, Mojtaba Amani, was also said to have been injured by the explosion of a pager according to Iran's Mehr news agency.
Hezbollah is one of the most heavily armed non-state groups in the world and forms part of the government in Lebanon, with dozens of MPs in parliament.
It is deemed a terrorist organisation by many, including some Western governments, and has played a significant role in the conflict between Israel and Hamas, exchanging fire with Israel since last October in parallel with the war.
Hezbollah leader Hassan Nasrallah previously warned the group's members not to carry mobile phones because Israel could use them to track their movements.
There was no immediate comment from the Israeli military.
A Reuters journalist saw ambulances rushing through the southern suburbs of Lebanon's capital Beirut amid widespread panic.
They also reported that, at Mt Lebanon hospital, motorcycles raced to the emergency room carrying people with severely injured and bloodied hands.
Residents said explosions were taking place even 30 minutes after the initial blasts.
Those injured by the exploding pagers included fighters and medics from Hezbollah, the news agency said.
Groups of people huddled at the entrance of buildings to check on the well-being of those they knew who may have been wounded, the Reuters journalist said.
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The security source said devices were also exploding in the south of Lebanon.
Lebanon's health ministry called on hospitals to be on alert to take in emergency patients and for people who own pagers to get away from them.
It also asked health workers to avoid using wireless devices.
AP said their photographers had seen hospital emergency rooms overloaded with patients, many with limb injuries and some in serious conditions.
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