Milad Eid, 66, is the fourth telecommunications official arrested this year in an alleged ring linked to Israel's intelligence service, the Israeli daily Haaretz reported quoting a Lebanese newspaper.
Eid is a senior technician at Ogero, the state-owned company that runs the country's land-line telephone. He retired last year and was then brought back to serve in the administrative position.
On 17 July, Lebanese security forces detained a third national suspected of spying for Israel via Lebanon's telecommunication sector, Agence France-Presse reported.
In response, Hezbollah leader Hassan Nasrallah said Israel had complete control over Lebanon's telecommunication sector, calling for convicted spies to be hanged amid a widening probe into acts of espionage.
Lebanon has arrested three suspects over the past month in an expanding probe into an alleged network of Israeli spies employed in the country's telecommunication sector, the newswire reported.
Two of the alleged spies, technician Charbel Azzi and Tarek Al-Rabaa, were likely accomplices at the company Alfa, one of Lebanon's two mobile service providers, a source close to the investigation told AFP. Al-Rabaa was reportedly a transmissions engineer.
The third suspect was arrested and "is a former employee in Lebanon's telecommunications sector," the source said.
Two Lebanese citizens have already been sentenced to death for "collaborating with Israel and providing information on targets," with one of the two found guilty of providing Israel with targeting information during the 2006 war, AFP reported.