Lebanese police say they have found evidence of collaboration with Israel
Lebanese security officials say an army colonel has been detained on suspicion of spying for Israel, the latest of about 30 such arrests.
There was no immediate comment by the Lebanese army about the report, which comes during a tense run-up to parliamentary elections next month.
More than 20 suspects have now been charged, some of them in their absence.
The latest to be charged are named as Ahmed Shibli, Jeryis Farah, and Jean Farah, described as a fugitive.
They have been charged with monitoring civilian and military installations and providing information to Israel about the movements of political figures.
Lebanon is at a state of war with its southern neighbour Israel.
Convicted spies face a possible life prison term with hard labour or the death penalty if found guilty of contributing to Lebanese loss of life.
Hassan Nasrallah, leader of the Shia political and militant movement Hezbollah, last week called for the death penalty for all suspects convicted of spying for Israel.
His party is contesting closely fought national legislative elections on 7 June and the espionage accusations have increased tensions between sharply divided political factions.
Opponents of Hezbollah have seized upon an unconfirmed report in Der Speigel magazine saying the party was involved in the assassination of former PM Rafik Hariri in 2005 - which Hezbollah officials have strongly denied.
Some suspects in the spy case are accused of helping Israeli forces identify Hezbollah targets during the 2006 war, which left Lebanese infrastructure devastated and caused more than 1,200 deaths, mostly civilians.
Those already in custody include a policeman, a former brigadier general and a housewife. Lebanon says sophisticated spying equipment was found in some of their homes. If convicted, they all face the death penalty.
Israel has made no comment on the accusations.