Arsenal fans have clashed with Paris St Germain supporters on the streets of Budapest ahead of tonight's Champions League final - as police prepare for further trouble.

Video footage showed a fight breaking out between rival groups on Király Street, with fans kicking and punching one another while flares were thrown. 

French fans could be heard shouting 'allez' during the altercation, with a police spokesperson saying officers are investigating 'group disorder' and working to identify the perpetrators.

Elsewhere, two British supporters have so far been arrested for disorderly conduct and damaging a vehicle.

It comes as some 4,000 officers will be deployed for tonight's fixture at the Puskas Arena, to keep visitors safe and try and prevent clashes between groups of rival supporters.

It is feared up to 10,000 fans could arrive in Hungary without tickets for the match, keen to be nearby for what could be a historic night for the Gunners. 

Arsenal have only appeared in the final once before in 2006, when they were beaten 2-1 by Barcelona.

But small scuffles and clashes between rival fans began as early as last night, with footage on social media showing groups of fans fighting in the streets.

Police said a group of fans lit and threw smoke flares shortly after midnight as others fought one another in Király Street. Officers are currently analysing the footage to identify those responsible.

Elsewhere at 4pm local time on Friday, a British man was arrested after becoming embroiled in a fight with two Portuguese men at one of the gates of the Champions Festival. All three were taken into custody and charged with disorderly conduct.

A second British citizen was later detained at around 11pm after climbing on to the top of a car and damaging it, police said. 

Even many hours before kickoff at 5pm UK time later, fans of both teams were already amassing in the streets on Saturday morning, many after a long night of celebrating and excitement late into Friday.

It is thought that by the time the match gets underway later, there will be as many as 45,000 extra football fans in the city, leading to the largest mobilisation of police in its history.

At a press conference this week, Major General Dr. János Zoltán Kuczik, commander of operations for the final warned: 'We will take decisive action if we encounter any behaviour that disrupts public order.

'It's no secret that having fans from London and Paris in Budapest at the same time poses a significant risk, but it is our job to minimize that risk.'

Security preparations for the last European game of the season began more than a year ago, with authorities taking advice from those in London and Paris, and officials also visiting last year's final in Munich to observe operations. 

It is the first time that Hungary have ever hosted the fixture. 

As well as ramping up security, the city has also laid on extra public transport and fan buses for both teams to transport their supporters. 

Closer to home, bars and fan zones across London are expected to be packed out later as supporters hope for a repeat of their side's recent Premier League success. 

Meanwhile in Budapest, Arsenal's final preparations are underway.

Speaking this week, manager Mikel Arteta said 'the ambition is bigger now,' after the side secured the top spot in England's top football league.

'We have won and now we want the second one. We have to aim for bigger destinations.

'I want the players to be so confident. The players want more. Going through those moments brings you a different kind of desire.

'You feel what it is like to win and you want to reproduce that feeling as often as possible.'

The fans are certainly feeling optimistic - straight off the back of the club's first Premier League trophy in 22 years, they will hope history is in the making.

Thousands took to the streets in Budapest last night to drink, dance and sing - and they'll be hoping there will be far more to come tonight. 

Many have faced long, complicated journeys to support their side, catching flights, trains and buses and taking indirect routes to ensure they arrived on time.

And whatever the outcome, the experts are agreed - spectators should expect a close game. 

Brazilian legend Cafu told the Daily Mail it is too close to call, but Arteta's side can certainly be 'really dangerous' for PSG.

'I don't know, it's really hard to know who will win. I can't say today if it's Paris or Arsenal,' said Cafu.

'Both teams have the same 11 [in quality] so it's really hard to know who will win.

'[Arsenal] are a really dangerous team. They're a team who knows how to play from set-pieces. They've had a fantastic competition, didn't concede too many goals. That's why I'm sure it's going to be a really big final.'