The two were arrested in Arlington, Virginia, where they had been living as a married couple with two young children.
According to court documents, Zottoli had claimed to be a US citizen, married to Mills, a purported Canadian citizen.
The two were charged with conspiracy to commit money laundering, and along with a third defendant, Mikhail Semenko, were charged with being foreign agents.
All three remained jailed after waiving their right to a detention or bail hearing during brief appearances in federal court on Friday.
They were among 10 people arrested and charged this week. Six other defendants had already appeared in US courts, and one was granted bail that will include electronic monitoring and home detention.
In Friday's court filing, prosecutors said Zottoli and Mills had $100,000 in cash and phony passports and other identity documents stashed in safe deposit boxes.
Semenko, who was in the US on a work visa, is not alleged to have used a false identity. But prosecutors said the FBI found computer equipment "of the type capable of being used for ... clandestine communications" in his home and a second apartment that he recently leased.
Meanwhile in the Cypriot capital of Nicosia, Loucas Louca, the justice minister, said it was unlikely that Christopher Metsos – the alleged 11th member of the spy ring – would be apprehended on the Mediterranean island because he was believed to have fled.
|Metsos disappeared after being granted
bail in Cyprus [AFP]
Metsos, 54, is wanted in the US on charges that he supplied money to the spy ring. He disappeared on Wednesday after a court in Cyprus – an island with close ties to Russia - freed him on bail.
Louca strongly defended Cypriot authorities' handling of the case, which left the government stung by rumours that it was complicit in Metsos' disappearance.
"If we wanted him [Metsos] to evade, as we have been accused, we wouldn't have tried as hard to arrest him in the first place," he said.
Russia's foreign ministry said that it had no reason to believe Metsos was in Russia.
"I do not have such information. You're knocking on the wrong door," Igor Lyakin-Frolov, a spokesman for the ministry, said.