At least 27 Gambians, including former army officers and top officials, have been arrested over last week's alleged coup plot.
President Jammeh took power in a coup and won elections in 2001
Six of them were shown on national television for almost two hours.
They admitted to planning to topple President Yahya Jammeh and appealed for mercy. One said he had been instructed to liaise with neighbouring Senegal.
President Jammeh, who seized power in 1994, has vowed to crush any attempt to overthrow him "without mercy".
"I will set an example that [will] put an end to... treachery and sabotage," he said at the weekend.
The alleged mastermind, former army chief of staff Mbure Cham, has reportedly fled to Senegal, which surrounds The Gambia.
Gambian authorities have asked Senegal to arrest him.
President Jammeh seized power in a 1994 coup and won a second term in 2001. He seeks re-election this year.
There have been a number of high-profile army sackings in the past year or so.
Late last year, Gambian police arrested three leading opposition figures in what the government said was part of a probe into a national security threat.