Rome, June 25 (IANS/AKI): Italian prosecutors are investigating an envelope addressed to Rome mayor Ignazio Marino containing a bullet and a letter threatening him and his family.

Postal workers at Rome's Fiumicino airport intercepted the envelope late on Wednesday and handed it over to police. Signed "Antonio Cavallo", the missive, written in broken Italian, urges Marino to drop a campaign against illegal street vendors and to deal instead with alleged corruption at Rome city council.

Marino announced this week that dozens of street stalls including snack trucks, souvenir sellers and florist stands will be forcibly relocated from Rome's historic centre to other areas of the city on July 10.

Street sellers who refuse to leave their pitches at the Colosseum, the Roman Forum, Pantheon and the Spanish Steps will be fined and could have their goods and vehicles impounded, the city council said.

Marino has rejected calls for his resignation amid a widening graft probe into alleged mob involvement in Rome municipal agencies.

The probe has led to the arrests of scores of people including a former city councillor, other politicians of various stripes, businessmen, officials and several underworld figures.

Rome's former conservative mayor Gianni Alemanno was among over 100 suspects implicated in the probe.