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 this weekend.
The FA Cup final, English Football League play-offs and the PGA golf Championship are also this week.
Manchester United cancelled a news conference today, due to be held prior to their Europa League final against Ajax in Stockholm tomorrow, 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 today, and the club closed its megastore, museum, cafe and stadium tours to the public.
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.
Football's European governing body Uefa announced a minute's silence will be observed prior to the final. The opening ceremony will also be considerably reduced as a mark of respect for the victims.
A Uefa statement said there was "currently no specific intelligence" to suggest Wednesday's game could be a target for further attacks.
There will also be a minute's silence before Saturday's Scottish Cup final between Celtic and Aberdeen at Hampden Park.
The Metropolitan Police says extra armed officers will be deployed at this weekend's major sports events in London, with a full review of the security and policing operations under way.
Cricket's Champions Trophy, which involves New Zealand, will take place from in early June at venues in Birmingham, London and Cardiff.