Metropolitan Police have arrested the fan, who is almost certain to face a lifetime ban from the Emirates Stadium.
The flashpoint occurred just hours after a fan attacked Jack Grealish in the clash between Birmingham and Aston Villa.
Emery said: ‘I don’t want that, but it’s not in my control. I think we need to enjoy the game but with respect.’
Solskjaer said: ‘There shouldn’t be a place for someone to be running on to the pitch. We don’t want to see that.’
An Arsenal spokesman said: ‘We utterly condemn the behaviour of the individual who ran on to the pitch and approached Chris Smalling.
‘We would like to apologise to Chris and United, and are pleased that he was apprehended and arrested. We will be working closely with the Metropolitan Police.
‘The individual will also be banned from Arsenal matches home and away. Our matchday staff receive ongoing training on incidents such as this.’