The IMF employee who opened the letter received hand and face injuries, and staff were evacuated.

It came after a parcel bomb meant for German Finance Minister Wolfgang Schaeuble was intercepted on Wednesday.

Greek far-left group the Conspiracy of Fire Cells claimed responsibility for sending that device.

French President Francois Hollande has noted a "similarity" between the two incidents.

"We are trying to establish the causes of what happened as part of an international investigation," he said.

IMF director Christine Lagarde condemned the "cowardly act of violence" against IMF staff.

'Firecracker'

Ms Lagarde said in a statement that the IMF was working closely with the French authorities to investigate the letter blast.

Greece's deputy minister for public order, Nikos Toskas, sad in a TV interview that the letter bomb was sent in the name of Vassilis Kikilias, a senior opposition politician from the conservative New Democracy party.

It bore a return address of an office in Greece "that is no longer in use", he said.

The letter bomb sent on Wednesday to Mr Schaeuble, which was intercepted and destroyed before it could explode, was sent in the name of Adonis Georgiadis, New Democracy's vice-chairman.

The explosive sent to the IMF was like a "big firecracker" and was sent by post, Paris police chief Michel Cadot said.

The office is located on the Avenue Iena, in a central district of the city centre near the Champs Elysees.

The IMF is one of three organisations, along with the European Commission and the European Central Bank (ECB), which bailed out the Greek government after it came close to defaulting on its debts.

In Germany, Mr Schaeuble is hosting the new US Treasury Secretary Steven Mnuchin.

The device sent to his ministry, which was intercepted in the mailroom, was designed to cause "severe injuries" when it was opened, local police said in a statement.