Sky News
Israel hasn't claimed responsibility, but all fingers will point to the Mossad, Israel's external intelligence agency famed for inventive and audacious attacks on its enemies. To do that, the attackers would have had to know at least the make and models of the individual pagers; to go further and co-ordinate the explosions on specific devices, it's likely the serial numbers would also be known, all of which points to another major security breach for Hezbollah. Alternatively the pagers themselves, all apparently part of the same batch, could have been tampered with before delivery.