Increased security will be in effect for tomorrow’s Chicago Marathon, the first major marathon staged in the United States since the tragic April bombing at the Boston race, organisers said.

Organisers have instituted baggage checks for runners and fans as well as restricting access to key points along the 26.2-mile route that winds through the downtown Loop, passes Lincoln Park Zoo and neighbourhoods such as Little Italy and Chinatown.

Chicago’s race is part of the World Marathon Majors series, which consists of Boston, Berlin, London, New York and Tokyo.

Enthusiasm in Chicago has not been dampened by the bombing in Boston, which killed three spectators and injured scores of others. Tomorrow’s race is sold out, with 45,000 participants registered, along with the usual 12,000 volunteers signed up to pass out water and assist at aid stations along the route.

Attendance is expected to be similar to the past, when some 1.7 million fans line the route encouraging runners.

The new measures will be evident before the race starts as runners must pick up their own participant packets, which includes their event bibs and timers. In previous years, someone else could pick up the packs for the runners.

The participant packs will include a clear plastic bag that runners must use for their race-day supplies, another new requirement. Marathon organisers said they will not accept any other bags at gear checks.

Police will step up the use of bomb sniffing dogs during the race as well as trying to keep the entire route of the race area clear of unattended baggage.

Chicago Police Department Superintendent Garry McCarthy said he had multiple conversations with his Boston counterpart in the run-up to the marathon.

Chicago organisers declined to say how many security personnel will be working at the race, or how many agencies will be involved, but noted that they have coordinated with the Department of Homeland Security, the Department of Justice as well as the Secret Service.

“I do feel like they are doing everything they can on security,” said Jenn Wisegarver, who is registered for the race and also ran the Chicago marathon last year.

The New York City Marathon scheduled for November 3 also is tightening security, including searching the bags of fans.