An employee at Naples' prefecture in southern Italy was lightly wounded on Tuesday after a letter addressed to the prefect exploded in her hands, Italian media reported.

Prefect Francesco Antonio Musolino's secretary, unnamed by the media, suffered minor burns to her hands and eyebrows and was taken to hospital, the reports said.

Musolino told reporters following the blast that the A4-sized white envelope had not contained toxins or radioactive material and police were examining a piece of paper found inside.

Letter bomb attacks are not infrequent in Italy. Italian far-left anarchist group FAI in particular has committed a string of attacks on European institutions and foreign embassies in Rome since 2000.

The group has widened its reach in recent years, with campaigns against tax inspectors, bankers, diplomats and a nuclear engineer.