Organizers and law enforcement officials are urging Boston Marathon spectators to leave backpacks and other bags at home. They also say crowds will be limited at the finish line where two bombs exploded a year ago.

Monday's 26.2-mile race is expected to attract 36,000 runners _ about 10,000 more than usual for the event _ and about 1 million spectators.

Officials said Wednesday that heightened security will include thousands of uniform police and hundreds of plainclothes officers, with about 100 video cameras monitoring the crowds.

Backpacks are not banned outright, but are strongly discouraged and could be searched.

Dave McGillivray, race director for the Boston Athletic Association, says he believes Boston will be the ``safest place on the planet'' on Monday. (Associated Press)