The Jan 24 suicide blast in Moscow's Domodedovo airport that killed 35 people was aimed primarily at foreigners, investigators said on Saturday.
"It was no accident that the terrorist attack took place in the international arrivals zone. Investigators believe that it was directed against, in the first place, foreign nationals," investigative committee spokesman Vladimir Markin said.
He said that the blast was carried out by a 20-year-old resident of the country's volatile North Caucasus region, but did not give further details.
Meanwhile, the Kommersant newspaper on Saturday reported that the bomb may have been triggered by a phone call.
Citing experts, the daily said that the plastic explosives used in the blast were likely to have been strapped around the waist of the suicide bomber.
Noting that parts of a cell phone were found at the scene of the explosion, the paper said it was "possible a phone call caused the blast".
The paper also said that the behaviour of the terrorist backs up this theory.
Video footage has revealed that he did not immediately set off the bomb, but walked around the airport for some 10 minutes.
"All this time the man wandered nervously about the arrivals zone, approaching and then moving away from those waiting. It's possible that one of his accomplices, thinking he would decide not to press the button, blew him up from a distance," the paper said.
No group has so far claimed responsibility for the attack.