"This plan was devised by a restricted group of conspirators composed of 11 army officers," the statement said. At their head was Baradine Berdei Targuio, president of the Chadian Human Rights Organization, it said.
Reuters was unable to reach Targuio, who is in prison.
Security services have been arresting people linked to the plot since Dec. 8 and have seized military equipment, the statement said.
Chad has been on edge since the battlefield death in 2021 of longtime ruler Idriss Deby, after which his son, Mahamat Idriss Deby, seized power.
Authorities have cracked down on dissent in recent months as demonstrators took to the streets to demand a quicker transition to democratic rule.
Some 50 people were killed in October in protests the government described as an "armed insurrection" but rights groups said was a pro-democracy demonstration.
