Officials pointed the finger at Israel in what appeared to be a sophisticated, remote attack that wounded more than 2,800 people at a time of rising tensions across the Lebanon border.

The Israeli military declined to comment.

A Hezbollah official who spoke on condition of anonymity told The Associated Press that the new brand of handheld pagers used by the group first heated up, then exploded, killing at least two of its members and wounding others.

Lebanon’s health minister, Firas Abiad, said at least nine people were killed and 2,800 wounded, 200 of them critically.

The son of Hezbollah lawmaker Ali Ammar was among the dead, a source close to the group told AFP, requesting anonymity to discuss sensitive matters.

The source had earlier said the son of another Hezbollah lawmaker, Hassan Fadlallah, was also killed, but later confirmed that the son was alive but injured.

Iranian state-run IRNA news agency said that the country’s ambassador, Mojtaba Amani, was superficially wounded by an exploding pager and was being treated at a hospital.

Photos and videos from Beirut’s southern suburbs circulating on social media and in local media showed people lying on the pavement with wounds on their hands or near their pants pockets.

Hezbollah leader Hassan Nasrallah previously warned the group’s members not to carry cellphones, saying that they could be used by Israel to track their movements and to carry out targeted strikes.

Lebanon’s Health Ministry called on all 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 photographers at area hospitals said the emergency rooms were overloaded with patients, many of them with injuries to their limbs, some in serious condition.

The state-run National News Agency said hospitals in southern Lebanon, the eastern Bekaa Valley and Beirut’s southern suburbs, all areas where Hezbollah has a strong presence, had called on people to donate blood of all types.

The news agency reported that in Beirut’s southern suburbs and other areas “the handheld pagers system was detonated using advanced technology, and dozens of injuries were reported.”

Education Minister Abbas Halabi announced the closure of schools and universities on Wednesday "in condemnation of the criminal act committed by the Israeli enemy".

The Hezbollah official who spoke 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.

Hezbollah blamed Israel for the blasts and warned it would be punished.

"We hold the Israeli enemy fully responsible for this criminal aggression," the group said in a statement, adding that Israel "will certainly receive its just punishment for this sinful aggression".

Lithium batteries, when overheated, can smoke, melt and even catch on fire. Rechargeable lithium batteries are used in consumer products ranging from cellphones and laptops to electric cars. Lithium battery fires can burn up to 590 C (1,100 F).

The incident comes at a time of heightened tensions between Lebanon and Israel.

The Lebanese militant group Hezbollah and Israeli forces have been clashing near-daily for more than 11 months against the backdrop of the war in Gaza.

The clashes have killed hundreds in Lebanon and dozens in Israel and displaced tens of thousands on both sides of the border.

On Tuesday, Israel said that halting Hezbollah’s attacks in the north to allow residents to return to their homes is now an official war goal.

Israel has killed Hamas militants in the past with booby trapped cellphones and it’s widely believed to have been behind the Stuxnet computer virus attack on Iran’s nuclear program in 2010.

* This story was edited by Ahram Online.