An envelope exploded inside the International Money Fund office in Paris on Thursday, slightly injuring one person, police sources told Reuters.

"An operation is underway for a person injured by a suspicious package with, according to preliminary information, a firework inside," a spokesperson for the Paris police told the Independent. 

Officials also told the Independent that threatening phone calls had been made to the IMF office prior to the attack, but a connection could not immediately be confirmed. 

The blast comes just one day after a Greek militant group claimed responsibility for a similar parcel bomb mailed to the office of German Finance Minister Wolfgang Schaeuble.

On the same day as the explosion, France issued a terror attack following a separate incident where gunshots were reported at a school in the southern town of Grasse.