Greater Manchester Police (GMP) are warning Manchester United fans travelling to Rome for Tuesday's Champions League quarter-final to co-operate with Italian security or face the consequences. Recent matches between United and Roma have been marred by crowd trouble, with rival supporters clashing inside and outside the Stadio Olimpico.

In an attempt to avert violence, the Italian authorities have organised transport to and from the ground for United supporters. GMP said anyone choosing to make their own way to the stadium - or those planning to buy tickets from touts - could be putting themselves in danger. The Italian police were heavily criticised for using batons on United fans during a game in Rome last April to stop missiles being thrown between rival sets of supporters. Eleven fans needed hospital treatment after the incident.

"We simply want to remind anyone travelling to Rome for the away leg that our counterparts take a robust stance on any kind of disorder," Superintendent John Graves, match commander for the Roma fixture, said. "In terms of getting to the game, free bus services will take supporters from a pre-arranged meeting place to the stadium.

"Anyone choosing to make their own way could potentially run the risk of coming into harm's way. Also, Italian police expect every Manchester United supporter to take advantage of this service. In preparation for this game, a voucher system has been set up which means fans will only be able to pick up their ticket at a designated ticket collection point 24 hours before the match. Supporters will have to produce their passports as proof of identity when they collect their ticket. Anyone attempting to get into the game with a forged ticket could be liable to arrest. We aim to continue the good work that has already been achieved in previous operations of this kind and prevent troublemakers ruining the reputation of genuine football fans."

Officers from Manchester recently flew to the Italian capital to discuss policing arrangements. They will also be monitoring British airports to target known troublemakers attempting to travel to Italy.

It is the fifth Champions League fixture between United and Roma in less than a year.

The two clubs met at the quarter-final stage in 2007, with violent scenes inside the Stadio Olimpico during the away leg in April. Three United fans were also stabbed outside the ground. Scuffles broke out outside Old Trafford during the second leg of that tie a week later, with 21 people arrested. The teams were also together in the group stage of this year's competition, which led to four Manchester United fans being jailed in Italy for their part in a fight between rival supporters in Rome last December.

They were part of a group which broke away from other fans on their way to the ground and became embroiled in clashes with Roma's notorious "ultra" fans at the Duca d'Aosta bridge.