UPDATE 10-FBI releases photos of two Boston bomb suspects
* Two men with backpacks captured in pictures before blasts
* Obama seeks to console Boston, nation at memorial service (Updates throughout)
By Aaron Pressman and Svea Herbst-Bayliss
BOSTON, April 18 (Reuters) - Investigators released pictures and video of two suspects in the Boston Marathon bombing on Thursday, enlisting the public's help in identifying two men wearing backpacks and baseball caps in the crowd minutes before bombs exploded near the finish line.
A 30-second video shows the men known only as Suspect 1 and Suspect 2 walking single file a few paces apart along Boylston Street in central Boston. One wears a dark baseball cap and sunglasses. The other has a white baseball cap turned backwards.
The time stamp is 2:37 p.m., roughly 13 minutes before two bombs backed with nails and ball bearings tore through the crowd, killing three people and wounding 176 including at least 10 who suffered amputations.
"Suspect 2 set down a backpack at the site of the second explosion," said Richard DesLauriers, the FBI special agent in charge in Boston. That image was kept from the public.
The FBI received a "high volume" of phone calls and web traffic after releasing the pictures, a bureau spokeswoman said. Statistics would be reported on Friday, she said.
The pictures were released a few hours after President Barack Obama delivered a stirring address to an interfaith service at a Boston cathedral, telling the city, "You will run again."
He promised resilience in a message to Boston and by extension an entire country unsettled by a momentous week.
Two days after the worst attack on U.S. soil since Sept. 11, 2001, a man was arrested on suspicion of mailing the deadly poison ricin to Obama and a massive explosion at a fertilizer factory devastated a small Texas community, killing at least 14 people and rattling windows up to 50 miles (80 km) away.
"As you begin this long journey of recovery, your city is with you, your commonwealth is with you, your country is with you," Obama said about a mile (1.6 km) from the Boston bomb site. "We will all be with you as you learn to stand and walk and, yes, run again. Of that, I have no doubt. You will run again."
Afterward, Obama met with bomb victims at Massachusetts General Hospital. Doctors at all the hospitals where victims were taken reported similar trauma for many patients: legs shredded by shrapnel and skin burnt by the blast.
PLEA TO THE PUBLIC
The FBI previously asked the thousands of people who congregated near the finish line to submit photos and video taken at the crime scene. That combined with media coverage of the marathon and surveillance cameras gave investigators an abundance of images to review.
The team discovered the first suspect "within the last day or so," DesLauriers told a news conference. That enabled them to connect him to the second man.
"Somebody out there knows these individuals as friends, neighbors, co-workers or family members of the suspects," DesLauriers said, while cautioning people that the men were considered armed and extremely dangerous.
A law enforcement official familiar with the investigation said that at various times over the last few days investigators thought they might have identified the men in the pictures. But all the tentative identifications proved uncorroborated, which is why the FBI decided to make the images public.
Investigators hoped the men would be identifiable within hours of the release of the pictures and video, a national security official said, also speaking on condition of anonymity.
Investigators were looking at the men for some period of time before deciding to make the videos public, and they had extensive video and still pictures to justify the FBI decision to label the two men as suspects, the official said.
At least one other person of interest who featured in crime scene pictures had been ruled out as a suspect. Also ruled out earlier in the week was a Saudi student who was injured in the attacks, the official said. (Additional reporting by Tim McLaughlin, Mark Felsenthal and Daniel Lovering in Boston and Deborah Charles, Mark Hosenball and Roberta Rampton in Washington; Writing by Daniel Trotta; Editing by Jim Loney)