A period of silence will be held before the start of the London Marathon on Sunday to pay tribute to those killed and injured in the bombings in Boston, race organisers have announced.

There will be a period of silence lasting 30 seconds before the start of the elite men's race and the mass start.

Organisers are also encouraging runners to wear black ribbons and a separate campaign has been launched for runners to cross the line with their hands over their hearts to mark the events in Boston that left three people dead and 150 injured, many seriously.

The build-up to the London Marathon and the race itself will go ahead as originally planned after a review of security arrangements by police, local authorities and race organisers.

Security for London is expected to be beefed up, although exact details have yet to be announced. The period of silence will be observed on all three London Marathon starts (red, blue and green) and will be signalled by a whistle at both the start and finish of the 30 seconds.

Race director Hugh Brasher said: "We want to show our support for our friends and colleagues in Boston at this difficult time for the global running community.

"We are determined to deliver an amazing event that will focus on one of the core pillars of the London Marathon, which is 'to have fun and provide some happiness and a sense of achievement in a troubled world'."

Organisers moved to reassure runners and spectators that their safety will be paramount at Sunday's race following the bombing at yesterday's marathon in Boston.

London Marathon chief executive Nick Bitel said: "The support we have been offered by our stakeholders and the wider running community has been outstanding. We have the full support of the Metropolitan Police, the Mayor's office and other authorities.

"We want to reassure our runners, spectators, volunteers and everyone connected with the event, that we are doing everything to ensure their safety and that the Virgin London Marathon 2013 is an outstanding success."