The pagers, deemed by Hezbollah to be safer than cellphones, were probably rigged with explosives before they were delivered to Lebanon, experts said.

Lebanon's Hezbollah was still handing its members new Gold Apollo branded pagers hours before thousands blew up this week, two security sources said, indicating the group was confident the devices were safe despite an ongoing sweep of electronic kit to identify threats.

One of the security sources told Reuters it was very hard to detect the explosives "with any device or scanner."