MOSCOW, Aug 16 (Reuters) - A passenger jet flying from New York to Moscow made an emergency landing in Iceland on Thursday after a caller claimed there was a bomb on board, a spokeswoman for Russian airline Aeroflot said.

"There was an anonymous call saying that there was an explosive device on the plane, which was already in the air," spokesman Irina Dannenberg said. "The pilot took the decision to land the plane and it landed safely. A search is being conducted."

A spokesman for Iceland's Keflavik airport said 253 people were on board the flight from New York's John F. Kennedy International Airport. A duty officer at Moscow's Sheremetyevo airport, the plane's destination, identified it as Aeroflot Flight 103.

"The bomb threat was made sometime earlier in the morning and at 5:30 a.m. GMT the plane decided to head for Keflavik ... The aeroplane landed safely at 6:27 a.m.," said Keflavik spokesman Fridthor Eydal, adding passengers may still be in the process of being taken off the plane.

Russian news agency Interfax, citing an unnamed source, said an anonymous phone call had been made to U.S. law enforcement agencies claiming that five suitcases were filled with explosive materials and that they would detonate upon arrival in Moscow.

Emergency teams also searched an aeroplane in the city of Voronezh, 500 km (300 miles) south of Moscow, for explosives on Thursday after an antonymous phone call was made to the city's airport, but no bomb was found, state-run RIA reported.

A suicide bomb blast in the international arrivals area at Moscow's Domodedovo airport in January 2011 killed 37 people. Islamist insurgents in Russia's North Caucasus claimed responsibility.

Suicide bombers identified as women from the North Caucasus blew up two planes on domestic Russian flights nearly simultaneously in August 2004, killing all 90 people aboard.