A paper bomb went off near the Italian parliament here as hundreds of taxi drivers protested over delays over an Italian legislation regulating app-based Uber and car-hire services.
The loud explosion on Tuesday shattered a large window in the 70th century Palazzo Macchi di Cellere, prompting shopkeepers to shutter their stores.
The blast spooked some protesters, who left the heavily policed Piazza di Monticitorio square, where the Italian Parliament is located.
The bomb exploded as Italy's Transport Minister Graziano Delrio met taxi union representatives in a bid to end a six-day strike by taxi drivers.
At least one demonstrator was injured during clashes with police outside the ruling Democratic Party's headquarters here.
Police charged at protesters who threw objects including glass bottles at officers and overturned tables and chairs at local bars and restaurants.
Videos were circulated on social media of a passer-by being beaten over the head with a baton, given first-aid by a reporter and taken to hospital in an ambulance.
Some protesters threw eggs at the Democratic Party headquarters and at Uber and car-hire drivers.
Drivers from all over Italy joined the Rome protest while wildcat strikes caused disruption to traffic in other major cities.
Taxi drivers said the legislation, which suspends until the end of 2017 norms to control car-hire and car-share services, helps Uber's "irregular" inroads into Italy's rigidly regulated taxi industry.
But supporters of the decree said Italians want greater choice in ride-sharing options.
Taxi services have been available to and from hospitals and for pregnant women and the disabled during the strike.