The Football Association will investigate the disturbances after Millwall's FA Cup victory over Leicester City on Saturday.

Shaun Cummings grabbed a last-minute winner for the hosts, but the result was overshadowed by post-match scenes as police were forced to deploy horses on the field to keep Millwall fans from attacking supporters in the away end.

Smirking Millwall boss Neil Harris refused to condemn the scenes, saying he didn't want "to be negative about anyone" on a day when his team had knocked out Premier League opposition.

The Metropolitan Police have confirmed that three supporters were arrested on Saturday, while video recording will be analysed to identify other offenders.

Millwall's win was overshadowed by the ugly post-match scenes (Getty Images)

On the final whistle an impromptu pitch invasion had been part of frenzied celebrations after such a dramatic finish, but once all players had left the field, a large number of fans turned towards the away end in search of trouble.

Dozens of bottles were thrown, among other projectiles, as the police and stewards struggled to get a hold on the situation.