An anonymous caller told New York police the plane carried five suitcases filled with explosives that would detonate upon arrival in Moscow, Russian news agency Interfax reported.
"The captain decided to make an emergency landing in Reykjavik. At the moment the passengers have been taken off the airplane," said Irina Dannenberg, spokeswoman for Aeroflot-Russian Airlines.
Vidir Reyinsson, chief inspector and head of the Civil Protection and Emergency Management department of the National Commissioner of the Icelandic Police, said the plane and all baggage would be searched after the 242 passengers and 11 crew members had gone through security checks, The Wall Street Journal reported.
"Everybody is safe and seems rather calm under the circumstances, no one seems very shocked," he said.
The diverted flight caused no major delays in flights arriving and departing from Keflavik airport, spokesman Fridthor Eydal said.