NIAMEY, Niger — Four of Niger's army officers arrested in December confessed to planning an attempt to overthrow the government, the defense minister said Wednesday.

Niger authorities arrested 12 soldiers and 11 civilians on accusations of planning an overthrow of the government in December, said Defense Minister Mahamadou Karidjo.

"At least four officers, including the mastermind Gen. Souleymane Salou, have confessed to wanting to overthrow the regime and have asked for clemency from President Mahamadou Issoufou and forgiveness from the people of Niger," said Karidjo.

Salou, a former army chief of staff, was found at his home by police with a list of 10 other officers involved, said Karidjo. Arrests have not yet been made, however, due to insufficient evidence, he said.

The arrested soldiers will face a military tribunal, Karidjo said, adding that the preliminary investigation is over.

"We want to resolve this matter of the coup once and for all, and in the interest of Niger," he said.

The arrests took place after a month-long surveillance operation that halted any attempt for a Dec. 18 takeover, the government has said.

After the arrests, the president warned that a political vacuum could lead to a takeover by Islamic extremists, referring to Mail's unrest in 2012. Niger has seen extremist attacks for years, most recently by Boko Haram.

Niger, which has a history of strongmen seizing power by force since its independence from France in 1960, is scheduled to have national elections on Feb. 21.