The Metropolitan Police say there has been no change London's threat level despite a 40% increase in the number of officers at today's Marathon.
The public are being urged to ensure they take good care of their belongings in order to avoid police responding to reports of unattended items.
The Boston bombings will not put off spectators or runners from taking part in tomorrow's London Marathon, the race's chief executive said.
Security has been stepped up for the 26.2 mile event in the capital with several hundred more officers set to line the streets for Sunday's marathon.
The race's chief executive Nick Bitel said: "After the terrible events in Boston we conducted a security review with the Metropolitan police and all the other agencies.
"As was announced yesterday, we have increased substantially the number of police officers who are going to be out there, going to be visibly reassuring people and putting in more search regimes and a number of other measures to ensure that it is as safe and fun as it always is."
He added: "I think the spectators won't be put off, we'll have a great day. There's some fantastic races, really competitive, and the numbers in terms of people running will be 35,500 - 36,000 as they would always be."
The Metropolitan Police have issued a statement on security plans for the London Marathon this weekend.
Chief Superintendent Julia Pendry said:
The Metropolitan Police has tweeted that it will be deploying an "increased and highly visible police presence" for the London Marathon this weekend.
The number of police officers on duty for the London Marathon has been boosted by 40% to provide reassurance in the wake of the atrocities in Boston according to Scotland Yard.
Chief Superintendent Julia Pendry revealed that there will be several hundred more officers out on the streets on Sunday, an increase of two-fifths on last year.
The senior officer, who has led the Marathon security operation for five years, said: "the most important thing is that there is no link between the Boston marathon and the London Marathon.
"However people need to feel reassured when they come out on Sunday.
"It is a good 40% increase on last year on numbers of officers on the ground. We've got more search dogs out, we have got more on high visibility patrols."
British athlete Iwan Thomas said what happened at the Boston Marathon last weekend has made him more determined to run at the London Marathon this weekend.
Home Secretary Theresa May has said the Metropolitan Police put more officers on duty at the London Marathon following the Boston bombs.
Iwan told Daybreak: "I'm really looking forward to Sunday, I suppose maybe, slightly in the back of my mind something could happen but in my eyes no. I'm gonna go out there and run".
Double Olympic gold medallist Mo Farah said he is comfortable with the security surrounding the London Marathon following the blasts in Boston.
Farah, who is set to run a half marathon this weekend, said, "For me, this is home, this is a great city ... and for what we did at the London Olympics, you shouldn't be worried at all".
When asked about the Boston Marathon bombings, Farah said, "You don't want see anything like that in this sport ... All my support goes to the people that got hurt and their families".:
There will be an increased police presence at the London Marathon this weekend in the wake of bombings at the Boston event, the Home Secretary told MPs today.
Theresa May said adjustments to security arrangements had been made to this weekend's race after the fatal explosions that tore through spectators watching the race in the US on Monday.
Giving evidence to the Home Affairs Select Committee, Mrs May said, "They've made some adjustments to policing. They've put in some increased policing for the marathon".
"The London Marathon is a regular event, the organisers have a good record in terms of venue security, such as you can for an event that covers 26 miles", she said, adding, "We're very conscious of safety and security needs".
London is ready to host a safe marathon in the wake of bombings at the Boston event, Culture Secretary Maria Miller told MPs.
Ms Miller said the 2012 Olympics and years of experience demonstrated that the Metropolitan Police and other security services have an excellent record at ensuring sporting events on the streets of the capital are safe.
The Culture Secretary said, "You will know from London 2012 last year, this country has a great deal of experience of ensuring our sporting events go well and that security is at the heart of the planning process".
"The London Marathon is no different", she continued. "The Minister for Sport [Hugh Robertson] met with the mayor yesterday again to go through the plans to make sure ... that we have the right security procedures in place".
During a brief formal statement, she said, "I'm delighted this weekend's runners here in London, a number of whom are MPs... will be asked to wear a black ribbon as a sign of respect and solidarity. A period of silence will be observed before the race begins".
Theresa May says that the Metropolitan Police have made a number of adjustments to their arrangements ahead of London Marathon following Boston bombs.
Ms May says that although there was no COBRA emergency meeting following Boston, she was briefed on Tuesday and "appropriate people have been sitting round the table."