Memorial ceremonies have begun in the US city of Boston to mark the anniversary of the deadly bombing at last year’s marathon, BBC reports.
US Vice-President Joe Biden and Massachusetts Governor Deval Patrick are attending a tribute at the Hynes Convention Center.
The flag will be raised and a moment of silence held at the finish line later.
Three people were killed and some 264 injured when two bombs exploded near the finish line at last year’s race.
Participants in Tuesday’s ceremonies include representatives from families of the victims and members of the emergency services, government agencies and civic organisations.
This year’s Boston Marathon is due to take place on 21 April.
Tuesday’s memorial events began with a wreath-laying ceremony at the site of the explosions, attended by the families of the three bombing victims – Martin Richard, Krystle Campbell and Lu Lingzi.
Relatives of university police officer Sean Collier, who was killed during a manhunt for the suspects, as well as state and local officials also attended the solemn ceremony.
Officials have told residents and visitors to expect a larger than normal police presence through the week leading up to the race.
However, Boston Mayor Martin Walsh said it would be “the Boston Marathon as it has always been”.
“Our goal is for everyone to enjoy the race,” he said.
City health officials say they have also made preparations to help those affected by the bombings cope with the anniversary.
“The first anniversary of a disaster is always difficult,” said Barbara Ferrer, director of the Boston public health commission.
In a statement, President Barack Obama said: “We send our thoughts and prayers to those still struggling to recover.
“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.”
“And when the sun rises over Boylston Street next Monday – Patriot’s Day – hundreds of thousands will come together to show the world the meaning of Boston Strong as a city chooses to run again.”
Bombing suspect Dzokhar Tsarnaev, 20, is due to stand trial in November. He has pleaded not guilty to 30 charges, of which 17 carry the possibility of capital punishment.
Prosecutors allege that he set off two pressure cooker bombs with his older brother Tamerlan, 26, who later died in a police shoot-out.