"Two French agents in our service and probably one of the spouses of these agents are accused of serious acts likely to be considered acts of treason, on suspicions of delivering information to a foreign power," Parly told CNews television.
Asked about unconfirmed reports that China was the foreign power in question, the minister said she "can't say much".
"France has partners but we live in a dangerous world, and unfortunately these types of things can happen," she added.
The two retired spies, one of whom was reportedly posted in Beijing, were arrested and indicted last December. They are being prosecuted for "delivering to a foreign power information that undermines the fundamental interests of the nation" and "compromising the secrecy of national defence".
"One of them has also been charged for direct incitement to the crime of treason," according to French reports quoting sources close to the investigation.
A third person -- believed to be a spouse to one of them -- has been indicted for "concealment of treasonable crimes" and placed under judicial control.
According to a statement by the Defense Ministry, the General Directorate for External Security (DGSE) intelligence agency alerted French prosecutors after uncovering the "extremely serious" behaviour of its former agents.
"The fact that we sounded the alert is proof of our vigilance," Parly said.
The minister said the compromised information handed by the agents while still in service for the DGSE "could undermine the security of the state".
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