Paris - A letter bomb exploded at the Paris offices of the International Monetary Fund on Thursday, injuring a secretary who suffered burns to her hands and face.Employees were evacuated from the building near the Arc de Triomphe in the heart of the capital after the late morning explosion which was caused by a firework.IMF chief Christine Lagarde condemned the incident as a "cowardly act of violence" and insisted the fund would continue its work "in line with our mandate," a statement from her office said."We are working closely with the French authorities to investigate this incident and ensure the safety of our staff."French President Francois Hollande called it an "attack", saying it showed the country was "still targeted".Since early 2015, France has been hit by a series of deadly attacks by Islamic extremists.The secretary, who works for an unnamed senior manager, suffered facial injuries caused by "shards, as well as a blast to the eardrums" but is out of danger, Paris police chief Michel Cadot said. "It appears to have been a firework or a big firecracker," he said, describing the device as "relatively rudimentary and nothing like a bomb". Armed police and soldiers earlier secured the area around the IMF offices and anti-terrorism prosecutors opened an inquiry into the incident.LinkedAlthough no link has been established at this stage, a Greek far-left group on Thursday claimed responsibility for sending a parcel bomb to the German finance ministry which was discovered in Berlin earlier on Wednesday. The incident occurred more than six years after the group waged a similar campaign targeting European officials.A Greek police source in Athens said "it is rather soon" to link the two incidents, adding: "We are cautious (and) remain vigilant."He noted that the letter sent to the IMF was destroyed in the blast, while the Berlin parcel bomb was made safe, with the sender's return address clearly marked on it.He said France had not yet sought cooperation from Greece over the incident.The Conspiracy of Fire Nuclei group claimed responsibility for the Berlin parcel bomb in a statement posted on an anti-establishment website, saying only that it had targeted Finance Minister Wolfgang Schaeuble's office.German police said they had discovered the "explosive" package at Schaeuble's office on Wednesday, a day before he was due to host his new US counterpart, Steven Mnuchin.Conspiracy of Fire Nuclei, which is blacklisted as a terror organisation by Washington, had in 2010 sent letter bombs to foreign embassies in Greece and to European leaders.Greeks blame Germany and the IMF for imposing years of public sector cuts and reforms in exchange for bailout packages needed to prop up the recession-hit country.