BOSTON — This year's Boston Marathon will have a "no bags" policy as part of stepped-up security following last year's deadly bombing, the Boston Athletic Association announced Wednesday.Marathon runners typically are allowed to bring bags or backpacks to keep personal items. Those bags are bused between the starting line in Hopkinton and the finish line in Boston.But this year, runners will not be allowed to bring backpacks or bags, which will also not be allowed in certain areas near the start or finish line, or along the 26.2-mile course.Runners will be given a chance to check gear on Boston Common on the morning of the marathon to allow them to have a change of clothing at the end of the race. The athletic association said it will provide clear plastic bags for that purpose.Twin bombs placed in backpacks near the 2013 finish line killed three people and injured more than 260. Prosecutors say two spectators were responsible.Dzhokhar Tsarnaev, 20, is awaiting trial and faces the possibility of the death penalty on 30 federal charges, including using a weapon of mass destruction. His brother, Tamerlan Tsarnaev, died following a gun battle with police several days after the marathon.State, local and federal law enforcement officials have been meeting for months to prepare a stringent security plan for this year's April 21 marathon.The new rules were outlined in an email sent by the athletic association to registered runners.The BAA said unregistered runners, known as "bandits," who traditionally jump into the race at various points along the course, will be strictly prohibited this year."Anyone on the course for any distance who has not been assigned, or is not displaying, an officially issued bib number from the B.A.A. is subject to interdiction," the association said in its email.Costumes covering the face or non-form-fitting, bulky outfits will also be prohibited.Runners were told they cannot bring backpacks or any similar item carried over the shoulder or handbags of any size. Those items will be prohibited from all marathon venues, including along the course, near the start or finish areas and at all official marathon events.Glass containers and any container larger than one liter will also be banned.The list of prohibited items for runners also includes strollers, suitcases and rolling bags, weight vests or any type of vest with pockets, except for lightweight running vests, which will be allowed.Props, including sporting equipment, military and fire gear, and signs or flags larger than 11 inches by 17 inches are also prohibited.The BAA said runners will be allowed to wear small fanny packs to carry food, medicine, identification, cellphones or other necessary small items. They can also bring water bottles, but they must be one liter or smaller. Organizers are discouraging runners from wearing headphones, but they will be permitted.Kurt Schwartz, the state's undersecretary for public safety, said officials are trying to maintain the excitement of marathon while at the same time ensuring the safety of the thousands of marathon participants and spectators."It will still feel like a great day and it will be a great day," Schwartz said."We are going to strike a good balance between public safety and security, and ensuring that this is a celebratory and festive event like it has always been."