ROME (AP) — A Manchester United fan was hospitalized after suffering a stab wound and nine people, including both United and Barcelona supporters, were arrested by Italian police in separate incidents ahead of the Champions League final in Rome.

As up to 50,000 United and Barcelona supporters converged on Rome for the highly anticipated game Wednesday night, huge numbers of police patrolled the city. While many fans peacefully flooded the cobblestoned streets of Rome, scattered episodes of violence were reported in and outside the Italian capital.

Police said that a United fan was taken to the Santo Spirito hospital after he was stabbed in the thigh in the early hours of Wednesday morning. They did not identify the victim.

The fan reported that he had been attacked by four people near his hotel in the Vatican area.

Separately, two United fans were arrested for assaulting bystanders and police in Campo de Fiori, a historical piazza and popular tourist hangout.

Police said the men, aged 19 and 45 but not identified, were drunk despite a ban on alcohol sales imposed by authorities in areas including the city center and near the stadium. "They will watch the match from a TV inside the Regina Coeli prison," said a police statement.

Three Barcelona fans were arrested after a police search in their car turned up blunt objects, including clubs and a javelin, police said. The three were traveling from Civitavecchia, a port near Rome where hundreds of Spanish fans had arrived by ship.

In yet another incident, four Italians were arrested in Ostia, on the coast near Rome, after they attacked an American, apparently mistaking him for a United supporter. The U.S. citizen was beaten up and had been stabbed in his thigh and backside, police said.

Some 30,000 fans from England and 20,000 from Spain arrived, largely on dozens of charter flights at Rome's airports.

Authorities have been monitoring hardcore fans of Rome's local teams amid concerns that they might seek to ambush visiting supporters. AS Roma fans especially were being kept under close watch as they clashed with United supporters in Rome in 2007, stabbing a number of them.

Rome Mayor Gianni Alemanno said that officials had warned leaders of the "ultras," or hardcore fans, not to create trouble.

With hours to go before the match, the fans flooded the city center, snapping pictures at the Colosseum and sporting the colors of their teams.

Hundreds attended Pope Benedict XVI's public audience at the Vatican, waving their flags and scarves before the pontiff. "We need his blessing," said Cristina Bargues, a 15-year-old student from Barcelona, wearing the blue-maroon scarf of the Spanish club.

The match referee, Massimo Busacca of Switzerland, greeted the pope at the end of the audience.

Some 67,000 people are expected to pack the Stadio Olimpico for club football's most prestigious event. Among attending VIPs were the Spanish royals and Britain's Prince William, who was invited by the English Football Association as the organization's president.

Thousands of law enforcement officials have been deployed around the stadium and in the city center, at airports and subway stops. Others were guarding Rome's monuments and other artistic treasures.

About 1,000 stewards will be deployed inside the stadium, and 30 police officers from England and Spain, some mingling with the fans in plainclothes, were also on hand to help the Italians.

Security officials say they expect some 5,000 ticketless fans, largely from England, to show up at the stadium, despite the authorities' warning that ticketing arrangements would be strict.

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Associated Press Writer Daniela Petroff contributed to this report from the Vatican.