Manchester United have expressed their shock at the terrorist attack in Manchester and held a minute's silence before their last training session before flying to Wednesday's Europa League final in Stockholm.
Greater Manchester Police have confirmed children are among the 22 killed and 59 wounded by a bomb that exploded after a concert by American pop star Ariana Grande at the Manchester Arena on Monday night.
United have also cancelled a scheduled press conference in Stockholm on Tuesday evening and Old Trafford is closed to the public.
In a statement, the club said: "Due to the tragic events in Manchester last night, and the effect that this has had on everyone here at the club and within our city, we have decided to cancel this evening's pre-match press conference.
"We are sure that, in the circumstances, you will all understand our position on this matter."
An earlier statement said everyone at United was "deeply shocked by last night's terrible events" and the club's "thoughts and prayers" went out to everyone affected, including children from their Manchester United Foundation partner schools who were attending the concert.
Messages of condolence, defiance and support have been coming in ever since news broke of the appalling incident, with many governing bodies saying they will take increased security measures at events.
In a statement released to Press Assocation Sport, a spokesperson for the Football Association said: "Fan safety is of paramount importance and we have robust security measures in place at Wembley Stadium.
"In collaboration with the Metropolitan Police and the local authorities there will be an enhanced security operation for all upcoming events. All supporters are encouraged to arrive for events at Wembley Stadium as early as possible for security checks and to avoid any delays in entering the stadium."
Wembley is set to host the FA Cup final between Arsenal and Chelsea on Saturday, the League Two play-off final between Blackpool and Exeter on Sunday and the Championship play-off final between Huddersfield and Reading on Monday.