Hezbollah has vowed to respond to an Israeli attack that killed multiple people and injured thousands across Lebanon on Tuesday when pagers belonging to members of the Iran-backed militant group exploded almost simultaneously, exposing a massive security breach and demonstrating the scale of Israeli intelligence, writes CNN.

A child was among at least nine killed in the blasts, which wounded about 2,800 people, Lebanese Health Minister Firass Abiad said. At least 170 people are in a critical condition, he said, though the nature of the other injuries is unclear.

The unprecedented attack risks further escalating tensions in the Middle East already heightened over Israel’s war against Hamas in Gaza. The extraordinary incident also underscores Hezbollah’s vulnerability as its communication network was compromised to deadly effect and follows a series of targeted assassinations against its commanders.

CNN has learned the explosions were the result of a joint operation between Israel’s intelligence service, Mossad, and the Israeli military. While the Israeli military has said it will not comment on the explosions, both Lebanon and Hezbollah have blamed it for the attack. Iran also blamed what it referred to as “Israeli terrorism”.

Speculation has mounted over how low-tech wireless communication devices could have been exploited. The New York Times reported Tuesday that Israel hid explosives inside a batch of pagers ordered from Taiwanese manufacturer Gold Apollo and destined for Hezbollah. A switch was embedded to detonate them remotely, it added. Gold Apollo’s founder and chairperson told reporters Wednesday that the pagers used in the attack were made by a European distributor. Hsu Ching-kuang said his firm had signed a contract with the distributor to use the Gold Apollo brand.