Boston - Boston began commemorating the marathon bombing on a quiet note on Tuesday as Mayor Martin Walsh and Roman Catholic Cardinal Sean O'Malley visited wreaths lain at the spots where the two bombs went off a year ago on Tuesday, killing three people and injuring 264.
Accompanied by an honor guard of police, a group of dignitaries that also included Massachusetts Governor Deval Patrick and the family of the youngest victim, 8-year-old Martin Richard, the mayor and the cardinal stopped twice along Boylston Street near the race's finish line.
They embraced and spoke softly as bagpipes played but made no public remarks ahead of a memorial where Vice President Joe Biden was due to speak.
President Barack Obama praised the city's response to the attack.
"Today, we recognize the incredible courage and leadership of so many Bostonians in the wake of unspeakable tragedy," Obama said in a statement. "One year later, we also stand in awe of the men and women who continue to inspire us - learning to stand, walk, dance and run again."
After the memorial, which also will feature musical performances, Boston will observe a moment of silence at 20:49 (SA time), the time the first bomb went off.
The April 15, 2013 blasts tore through the crowded finish line of the world-renowned race, injuring spectators, volunteers and athletes, in the worst mass-casualty attack on U.S. soil since the Sept. 11, 2011 attacks that killed some 3,000 people.
This year's race, set for April 21, will take place under heightened security, with the 36,000 runners and tens of thousands of expected spectators facing new restrictions, including bans on carrying backpacks into the race corridor.
Federal prosecutors say that a pair of ethnic Chechen brothers, Dzhokhar and Tamerlan Tsarnaev, carried their homemade pressure-cooker bombs to the finish line in backpacks.
The bombs killed Martin Richard, Krystle Campbell, 29, and Chinese national Lu Lingzi, 23.
Three days after the attack, the FBI released pictures of the suspected bombers and asked for the public's help in finding them. That prompted the Tsarnaev brothers to attempt a hasty flight from Boston, which began with them shooting dead Massachusetts Institute of Technology police officer Sean Collier, prosecutors said, in an unsuccessful attempt to steal his gun.
The resulting police chase ended in a gunbattle in the Boston suburb of Watertown. Tamerlan, 26, was killed; Dzhokhar, now 20, escaped before being captured on April 19.
The brother is awaiting trial on charges that carry the possibility of execution if he is convicted.