Two planes said to be taking part in an exchange of spies between Russia and the US have landed in Austria's capital, Vienna.
The 10 Russian agents were earlier deported from the US after a court hearing at which they admitted spying for a foreign country.
Russian President Dmitry Medvedev pardoned four people convicted of espionage in Russia.
They reportedly submitted a plea for pardon admitting their guilt.
Reports said that a Russian emergencies ministry plane had landed at Vienna airport at about the same time as the Vision Airlines jet from New York.
Television pictures showed the two aircraft parked side-by-side on the runway.
The BBC's Bethany Bell in Vienna says there is no official word on how the swap will take place, but adds that in the past third parties have been used to help with such exchanges.
A senior Russian official was quoted by Agence France-Presse news agency as saying the Russian agents were expected to arrive back in their homeland on Friday
The lawyer for Igor Sutyagin, one of those released by Russia, has confirmed that his client has left Moscow, Austrian media say.
'Conspiracy'The 10 Russian agents earlier pleaded guilty in New York to "conspiracy to act as an unregistered agent of a foreign country". More serious money laundering charges against them were dropped.
Their New York court appearance was the first time they had all appeared in public together since being arrested last month.
Prosecutors said the accused had posed as ordinary citizens, some living together as couples for years, and were ordered by Russia's External Intelligence Service (SVR) to infiltrate policy-making circles and collect information.
BBC Washington correspondent Kevin Connolly says there is broad agreement in the US that the agents are being deported swiftly because neither government wants this to damage attempts to reset their often prickly relationship.
Court documents revealed the real names of five of the Russians involved:
- "Richard Murphy" and "Cynthia Murphy" admitted they were Russian citizens named Vladimir Guryev and Lydia Guryev
- "Donald Howard Heathfield" and "Tracey Lee Ann Foley" admitted they were Russian citizens named Andrey Bezrukov and Elena Vavilova
- "Juan Lazaro" admitted that he was a Russian citizen named Mikhail Vasenkov
"Michael Zottoli" and "Patricia Mills" had admitted earlier they were Russian citizens named Mikhail Kutsik and Natalia Pereverzeva, Anna Chapman and Mikhail Semenko had apparently operated in the US under their own names, while Vicky Pelaez was born in Peru.
An 11th suspect known as "Christopher Metsos" went missing after being released on bail in Cyprus, where he had been arrested.
The Kremlin named the four released in Russia as:
- Igor Sutyagin, a nuclear scientist jailed in 2004 for spying for the CIA
- Sergei Skripal, a Russian military intelligence officer convicted of spying for the UK in 2006
- Alexander Zaporozhsky, a former employee of Russia's foreign intelligence service jailed for espionage in 2003
- Gennadiy Vasilenko, reportedly a former KGB agent
The US state department said after the hearing that there would be "no significant national security benefit" in sentencing the 10 to lengthy jail terms.
"The network of unlawful agents operating inside the United States has been dismantled," spokesman Mark Toner said.
"The United States took advantage of the opportunity presented to secure the release of four individuals serving lengthy prison terms in Russia, several of whom were in poor health".
The lawyer for Anna Chapman played down the importance of the Russian group's espionage in the US.
Robert Baum told Associated Press: "None of the people involved from my understanding provided any information that couldn't be obtained on the internet".
A lawyer for Vicky Pelaez, John Rodriguez, said a Russian official had told his client she would receive $2,000 a month for life and free housing in Moscow, but added she would be allowed to leave Russia if she wanted to. Mr Rodriguez indicated Ms Pelaez would return to Peru.
The Russian foreign ministry issued a statement saying that the exchange by Russia's Foreign Intelligence Service and the US Central Intelligence Agency was being conducted in the context of "overall improvement of the US-Russian ties and giving them new dynamics".
One of the Russian prisoners pardoned by Moscow, nuclear specialist Igor Sutyagin, was earlier transferred to Moscow from a prison near the Arctic Circle.
He reportedly told his family in Moscow that he would be flown to Vienna and released as part of a deal between the US and Russian governments.
