Sporting events and venues in England are conducting major security reviews after 22 people were killed in an attack at Manchester Arena.
The Great City Games, an open and free event for the public, is due to take place in Manchester on Friday.
Organisers said the event will go ahead as planned, but a decision on Sunday’s Great Manchester Run “is expected in the next 24 hours”.
An eight-year-old girl was among those killed in Monday’s suicide bombing at Manchester Arena, at the end of a concert by US singer Ariana Grande.
Prime Minister Theresa May said the UK terror threat level has been raised to its highest level of ‘critical’, meaning further attacks may be imminent.
Manchester United cancelled a news conference on Tuesday, due to be held prior to their Europa League final against Ajax in Stockholm on Wednesday, and will wear black armbands for the match.
The club said: “Our thoughts are with the victims and their families at this terribly difficult time.”
United’s players held a minute’s silence at training on Tuesday, and the club closed its megastore, museum, cafe and stadium tours to the public.
A staff event scheduled for Wednesday has been cancelled by executive vice-chairman Ed Woodward.
Manager Jose Mourinho said: “We are all very sad about the tragic events; we cannot take out of our minds and our hearts the victims and their families.
“We have a job to do and we will fly to Sweden to do that job. It is a pity we cannot fly with the happiness that we always have before a big game.
“I know, even during my short time here, that the people of Manchester will pull together as one.”
