A man carries newspapers featuring the Boston marathon blasts on the front page, while waiting to cross a road in central London, Tuesday, April 16, 2013. British police are reviewing security plans for Sunday's London Marathon, the next major international marathon, because of the bombs that killed three people at the marathon in Boston Monday. (AP Photo/Sang Tan)
World responds to Boston bombing
In the wake of the Boston attacks, several countries, including France and Great Britain, have ordered local authorities to step up security and reinforce measures already in place.