The deadly explosions at the Boston Marathon reverberated on both sides of the Atlantic as cities from Los Angeles to London saw a surge in security.
The White House, New York's Times Square, and the preparations for former Prime Minister Margaret Thatcher's funeral in London all had enhanced and intensified law enforcement presence after Monday's two blasts in Boston.
Police in Los Angeles, Washington, D.C., Detroit, San Diego and Las Vegas monitored landmarks, government buildings, transit hubs and sporting events. Law enforcement agencies also urged the public via Twitter and Facebook to report suspicious activity to the police.
British police were also reviewing security plans for Sunday's London Marathon — the next major international race — because of the bombs that killed three people and injured more than 140 in Boston.