Ten people who spied for Moscow in the US have arrived in Russia after being deported as part of the biggest spy swap since the Cold War.
They were driven away from a Moscow airport in a convoy of vehicles hours after the exchange in Vienna, Austria.
A US jet which picked up four Russians freed by the Kremlin has landed in Washington.
It reportedly dropped two of them off in the UK en route.
Washington said the spy swap had been completed successfully.
Without mentioning the actual swap, Russia said the 10 people freed by the US had been released "for humanitarian considerations", and it noted "the general improvement of Russia-US relations".
The exposure of the deep-cover Russian spying ring last month had raised questions about how genuine was the Kremlin's commitment to good relations with the White House - the Obama administration's so-called "reset".
It has emerged that the US considered making the swap even before it broke up the Russian spy ring last month.
In another development, the UK's Home Office said it was urgently reviewing whether to deprive one of the Russian spies, Anna Chapman, of her British passport.
She has the passport because of her previous marriage to a Briton.
The 10 Russian agents, who include the Peruvian partner of one of the men, were jetted out of the US after admitting to spying illegally for a foreign country.
Their plane landed in Vienna around the same time as a Russian government plane carrying four released prisoners, three of whom have convictions for spying against Russia.
One of those with an espionage conviction is nuclear specialist Igor Sutyagin, who has always insisted that information he provided was available from open sources.
The BBC's Bethany Bell in Vienna says the spy swap took place in broad daylight.
They were parked close to the main passenger terminals, rather than in a secluded part of the airport, she says.
Commercial jets continued to take off and land during the swap.
The rest of the airport was full of holidaymakers and business passengers, many unaware of the major diplomatic incident happening so close at hand, our correspondent adds.
Then the two planes took off again after 90 minutes, the Russian jet leaving first, bound for Moscow's Domodedovo airport.
The American plane made a brief stopover at RAF Brize Norton in Oxfordshire, England, where some people were seen getting off.
Unnamed sources told news agencies that two of the four Russians were dropped off before the plane headed across the Atlantic.
It landed at Washington Dulles airport later on Friday.
A White House official has revealed that the Obama administration was considering a spy swap well before the 10 were arrested on 27 June.
White House officials were first briefed on the spy ring in February, while President Barack Obama was made aware of the case on 11 June, the source said.
"The idea of a swap was discussed among the administration's national security team before the arrests were made," the source added.
According to the same official, the US itself chose the names of the four men to be freed by Moscow.
Its decision was based on "humanitarian concerns, health concerns, and other reasons".
Peter Earnest, a former CIA officer, welcomed the release of the four.
"This sends a powerful signal to people who co-operate with us that we will stay loyal to you," he told the Associated Press news agency.
"Even if you have been in jail for years, we will not forget you."
The assumption is that the 10 spies now in Russia will be debriefed by the authorities and will be kept away from the media for the time being, the BBC's Rupert Wingfield-Hayes reports from Domodedovo.
The Kremlin's refusal to acknowledge the spy swap has even taken place is perhaps an attempt to hide its own embarrassment at the discovery of its spy ring in the US, our correspondent says.
Moscow has reportedly promised the 10 incomes and housing, and to assist in bringing their eight American-born children to Russia.
The Peruvian may want to go back to her country but the others now face starting all over again in a country that some have not seen for 10 or even 15 years.
Russian TV and radio gave the spy swap blanket coverage on Friday after largely ignoring the story the previous day.
Reporters and news readers were upbeat about the exchange, presenting it as a sign of an improvement in relations between the big powers.
They spoke in neutral terms about the prisoners on both sides, merely listing the charges they had faced.
But ordinary Russians took little satisfaction from the agents' undercover exploits, the Associated Press reports from Moscow.
"They obviously were very bad spies if they got caught," said Sasha Ivanov, a businessman walking by a Moscow train station.
"They got caught, so they should be tried."