(VOVworld) - Italy has raised its security alert to the maximum level of grade 4 as the Holy Year of Mercy started on Tuesday and will run until November 2016.

Pope Francis leads a mass to mark opening of the Catholic Holy Year, or Jubilee, at the Vatican. Photo: Reuters

Italian authorities have deployed about 2,000 police officers across Rome and ordered a no-fly zone over the city centre due to safety concerns related to potential terrorist attacks in the wake of the 13 November shootings and bombings in Paris. Hundreds of faithful queued outside the Vatican early in the morning, waiting to be allowed inside St Peter's square for the opening ceremony. Access to the site was heavily controlled, with police conducting body searches on pilgrims, including priests and nuns, who also had to go through dozens of metal detectors set up for the occasion. Streets around the Vatican were closed to traffic, and setting off fireworks was banned, as was the transport of fuel and any potentially explosive material across the city.