TWELVE people were arrested as tensions ran high during Liverpool's clash with Manchester United on Saturday.

Bricks and concrete slabs were hurled at police officers as United fans were escorted away from the ground.

And on the pitch, players were subjected to verbal and physical abuse when fans threw objects and insults at them from the stands.

Liverpool fans were widely criticised yesterday for taunting United star Alan Smith, as he lay in agony on a stretcher after suffering a horrific leg break.

But yesterday, Merseyside Police said its massive security operation had been a success and the day had passed without major incident.

The match was a potential flashpoint after the FA Cup violence between Everton and Man Utd fans last year, when 30 people were arrested during clashes between 300 fans.

Before the match, police led a "risk group" of 350 United supporters from the city centre to Anfield, arresting eight for disorder and drugs offences.

Following the game, United fans were kept inside the ground for about 20 minutes to allow Liverpool supporters to disperse, during which time police intervened in scuffles in the Anfield Road away end.

Police, including some on horseback, then escorted a group of 1,000 United fans to Lime Street station, when officers were pelted with heavy objects by a group believed to be Liverpool supporters.

A Merseyside Police spokeswoman said: "There was no disorder between Liverpool and Manchester United supporters.

"However, Merseyside Police officers did come under attack from a group of about 150 people who had waited for the escort to pass.

"Missiles, including bricks and concrete slabs, were thrown at officers on Walton Lane. Officers from the force's Matrix team dispersed the crowd."

The spokeswoman said a total of 12 people were arrested in connection with the match for a range of public order offences, and no officers were injured.

Unconfirmed reports suggested a gun was wielded in one exchange between fans in Stanley Park following the match, although police said the incident had not been reported.

Superintendent Chris Arnitt said: "This was always going to be a difficult fixture for us to police but we are delighted with the success of the operation.

"Officers demonstrated great bravery and professionalism when dealing with, at times, a threatening situation."

At the start of the match, coins were thrown at Liverpool captain Steven Gerrard as he took a corner, while United's Gary Neville was the target of a number of missiles, including a beefburger.

When United star Alan Smith broke his leg after falling awkwardly in a block tackle with John Arne Riise, some Liverpool fans changed the words of a regular Anfield chant, singing: "John, Arne Riise, I wanna know how you broke his leg."

After lengthy medical attention, Smith was later applauded off the pitch by supporters from both sides.

United manager Sir Alex Ferguson described the injury, which destroyed Smith's chances of playing in the World Cup, as "the worst I've seen". Striker Ruud van Nistelrooy held his head in his hands in horror and other players looked shaken.

Les Lawson, Merseyside branch secretary of the Liverpool Supporters' Club,, said last night: "Originally they were singing it as a tongue-in-cheek song and they were expecting him to get back up.

"But, from where I was standing in the Kop, as soon as people realised how serious it was, they stopped singing."

He added: "After the match, I wrote a letter to Alan Smith, expressing our get well wishes. You don't like seeing any player receive a serious injury."

graham.davies@liverpool.com