File picture: AP Photo/Riccardo De Luca

Rome - A public transport bus accidentally caught fire in central Rome on Tuesday, causing scenes of panic as people initially feared a terrorist attack.

The number-63 bus went up in flames in Via del Tritone, just off the Trevi Fountain, a major tourist hotspot, just before 10.30 am (0830 GMT), the national fire service wrote on Twitter.

The passengers and the driver were evacuated safely but a woman who was walking near the bus suffered light injuries and was hospitalized, the ANSA news agency said.

A woman who was near the scene, and who did not want to give her name, told dpa that she heard a loud explosion and saw a huge cloud of smoke and people running away, screaming.

ATAC, the local bus company, said the bus was 15 years old and was "completely destroyed." An internal enquiry will investigate the causes of the accident, it added.

The fire cast a spotlight on the dire state of public transport in Rome. ATAC was declared insolvent last year, after making losses of 1.4 billion euros (1.66 billion dollars) from 2009-2016.

ANSA quoted trade unionists as saying that about 30 per cent of ATAC's 1,900-2,000 buses are not roadworthy, and that the average age of its fleet is 14 years, against a European standard of 7-8 years.

"It's the umpteenth bus that's gone up in flames in the city. We estimate that this kind of thing happens once a month," Michele Frullo of the USB union told ANSA.