A Boston police officer applauds runners as they approach the finish line of the 118th Boston Marathon in Boston, Massachusetts, April 21, 2014. [Photo/Agencies]

"I showed up, I'm back, and I am going to finish what I didn't finish last year,"said Mary Cunningham, 50, of St. Petersburg, Florida, who was stopped a mile short of the finish line by the explosions last year.

Sabrina Dello Russo, 38, of South Boston, was running her first marathon for a good friend, Roseann Sdoia, who lost her right leg in the bombing.

"She is my inspiration from day one last year when I saw her in the ICU. Every run I do, she is in the back of my head, and she will be keeping me going today,"Dello Russo said.

While Gov. Deval Patrick said there had been no specific threats against the race or the city, spectators at the 118th running of the world's oldest annual marathon had to go through tight checkpoints before being allowed near the starting and finish lines.

Fans hoping to watch near the finish line were encouraged to leave strollers and backpacks behind. Police set up checkpoints along the marathon route to examine backpacks, particularly outside subway station exits. And runners had to use clear plastic bags for their belongings.

More than 100 cameras were installed along the route in Boston, and race organizers said 50 or so observation points would be set up around the finish line to monitor the crowd.

Among the spectators cheering runners near the finish line was Jeff Bauman, who lost his legs in the bombing. It was the first time he had returned to the area since the attack.

"It feels great"to be back, he said. "I feel very safe."

Race organizers expanded the field from its recent cap of 27,000 to make room for more than 5,000 runners who were still on the course last year at the time of the explosions, for friends and relatives of the victims, and for those who made the case that they were "profoundly impacted"by the attack.

Kenya's Rita Jeptoo won the women's race in a course-record 2 hours, 18 minutes, 57 seconds, defending a championship from last year. She had been hoping this year for a title she could enjoy.

"It was very difficult to be happy. People were injured and children died,"she had said of last year's marathon. "If I'm going to win again, I hope I can be happier and to show people, like I was supposed to last year."

On Twitter, President Barack Obama congratulated Keflizighi and Shalane Flanagan, the top American finisher among the women, "for making American proud!"

Other runners were expected to remain on the course for several hours after the winners crossed the finish line. Last year, the bombs went off at 2:49 p.m., as spectators crowded around the finish the line to cheer the still-arriving runners about five hours into the race.

Dzhokhar Tsarnaev, 20, is awaiting trial in the April 15, 2013, attack and could get the death penalty. Prosecutors said he and his older brother _ ethnic Chechens who came to the U.S. from Russia more than a decade ago _ carried out the attack in retaliation for U.S. wars in Muslim lands.

Tamerlan Tsarnaev, 26, died in a shootout with police days after the bombings.

One runner Monday, Peter Riddle, a 45-year-old Bostonian, said he suffered post-traumatic stress disorder from being at the finish line last year.

"I did a lot of talking this year, but running has helped me resolve a lot of things in my head,"he said. "Running the marathon this year and running down Boylston Street will help me find peace and help me move forward."

Associated Press writers Jimmy Golen and Rik Stevens in Boston and Paige Sutherland in Wellesley contributed to this report.

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