Police intercepted a car packed with explosives in central Moscow on Saturday and said they had thwarted a terrorist attack, Russian media reported.
A suspect arrested at the scene told investigators he was being paid $1,000 to take the car to a major thoroughfare used by President Vladimir Putin to travel to and from the Kremlin, news agencies and television said, quoting the security forces.
The suspect later died from a heart attack in hospital after questioning, Interfax news agency quoted officials as saying.
Some reports suggested the planned attack might have targeted a museum on the road where Moscow Mayor Yuri Luzhkov had invited mayors from other major cities at the weekend.
The incident was prominently reported on television newscasts following a string of attacks by Chechen rebels in recent weeks.
These have included a school siege in southern Russia during which more than 320 hostages died, and near-simultaneous twin plane crashes that killed 90 people.
