Maria Butina clutched bouquets of flowers and exclaimed that "Russians don't surrender" as she arrived in Moscow on Saturday after serving nine months in a US jail for acting as a Russian government agent.
Butina flew into Moscow's Sheremetyevo airport after being deported from Miami following her release on Friday, AFP journalists said. She had been held in Florida's Tallahassee prison.
"I didn't give up because I know I simply didn't have the right," Butina told a waiting crowd of journalists. "Russians don't surrender!"
She was arrested in July 2018 on allegations of engaging in espionage.
In December, Butina entered a plea deal on a charge that she acted as an illegal, unregistered foreign agent, and was sentenced to 18 months in prison, half of which was credited as already served.
"I am very happy to be home. I am very grateful to everybody who supported me, to the Russian citizens who helped me and wrote letters," an emotional Butina told reporters on her arrival.
"Many thanks to the foreign ministry and to the diplomats who daily fought my corner," added Butina, who was handed several bouquets of flowers by wellwishers as her father and foreign ministry spokeswoman Maria Zakharova escorted her through arrivals.
Butina, a 30-year-old from Siberia, used ties with the NRA firearms lobby to help build a network of high-level Republican contacts.
She attended political rallies and NRA conventions, often with her powerful Moscow sponsor Alexander Torshin, a politician close to President Vladimir Putin.
Those efforts brought her into contact with President Donald Trump before his 2016 election, as well as with one of his sons, Donald Trump Jr, whom she reportedly met at a dinner during the 2016 NRA annual convention.
Butina was the only Russian arrested and convicted in a three-year investigation of Moscow's interference in US politics.
After her arrival, Kremlin-funded RT television showed her travelling in a minibus with diplomats and talking of "the horror that I found myself in," while jailed in America.
"Absolutely everyone hated me, everyone," she said, describing watching news reports about herself while in prison in Washington that "showed the ugliest pictures of me and made some kind of TV show out of it."
"It was very hard," she added.
- 'Contrived and fabricated' -
Moscow decried her case as being politically-motivated.
The Russian foreign ministry made her into a cause celebre, placing a picture of her with the word "Free Butina" at the top of its social media pages.
On Saturday, the ministry posted a photograph of Butina with the caption "Welcome home, Maria!"
It said diplomats had tirelessly spoken out on her case, calling the charge on which she was convicted "absolutely contrived and fabricated."
Her father Valery Butin at the airport thanked the foreign ministry for its "moral support."
- 'Spot and assess' targets -
Even with her release, her case remained murky. US prosecutors watered down early allegations that she was an operative of Russia's intelligence agencies, and described her only as funded by senior politician Torshin.
But they maintained that she had a mission to infiltrate US political circles in an operation to "spot and assess" potential espionage targets.
Part of that involved becoming the live-in girlfriend of a mid-level Republican operative who sponsored her as a graduate student at American University in Washington.
- Spy swap? -
Her future in Russia remained unknown. There was some speculation that Moscow's arrest of an American, Paul Whelan, last December for alleged espionage was a tit for tat and that her release could lead to his.
But Whelan's brother David told AFP this week that it appeared Moscow could want much more in return for Paul Whelan's release, including a possible swap for other US-jailed spies and the reopening of two Russian-leased estates in New York and Maryland that were forced to close in 2017 in retaliation for Russian election meddling.
Nevertheless, Whelan tweeted on Friday: "I wish the very best for Ms. Butina and much joy for her reunion with her family. We look forward to the same opportunity with Paul in the future."