A booby-trapped letter exploded at the French office of the International Monetary Fund (IMF) yesterday, injuring one person.
French President François Hollande described it as a "terrorist attack".
The incident came as a Greek anarchist group claimed responsibility for a failed letter bomb sent to the German finance ministry on Wednesday.
IMF director Christine Lagarde, who is French, said in a statement that she was informed about the explosion while on a trip to Germany.
"I condemn this cowardly act of violence and reaffirm the IMF's resolve to continue our work in line with our mandate," she said.
Police said one woman was lightly injured when the package, containing what appeared to be a home-made "pyrotechnical device or a large firecracker", blew up at the offices in central Paris.
The victim, an assistant to the director of IMF's offices in Europe, was burned on the hands and face.
Paris police chief Michel Cadot said the package was addressed to the secretariat of the IMF's France representative in Paris and "exploded when the secretary was opening it".
"This was a pyrotechnical device, or a large firecracker. It was pretty home-made, and was in no way a bomb," he added. Mr Cadot said that the IMF had received "a few threats in recent days".
There is no indication yet whether there is any link between this booby-trapped package and one sent to the Germany finance ministry.
Addressed to Wolfgang Schaüble, the finance minister, the package came from Greece and contained "an explosive mixture" that could have caused "considerable" damage, police said. It was destroyed before it could explode.
The Greek group that claimed responsibility, Conspiracy Cells of Fire, claimed in an online posting yesterday on a Greek left-wing website that the attack was part of a campaign by international anarchist groups.