Security officials in the US have stepped up security for the first Boston marathon since a bomb attack on last year's event.

It's exactly a year since two bombs exploded close to the finish line, killing three people, including a child, and wounding hundreds of others.

Around 4000 police officers will be on duty for the event, including 500 undercover. There'll also be thousands of volunteers helping with security, first aid and management.

One alleged perpretator of the bombing was killed during a shoot-out with police and another, Dzhokhar Tsarnaev, is due to stand trial.

Al Jazeera's Alan Fisher reports from Boston.

Source: Al Jazeera