Three people, including an eight-year-old boy, were killed and 144 injured as terror returned to the US with two powerful explosions striking the world’s oldest annual marathon in the city of Boston. President Barack Obama vowed that those responsible would feel the “full weight of justice”.

The two successive blasts rocked the Boston Marathon finish line on Monday afternoon. And when the smoke cleared after the blasts in Boston’s Back Bay section, dozens of victims lay in the street, some unconscious, some grievously injured, including some whose limbs had been torn off by the blast.