The FBI has released photographs and video footage of two suspects in the Boston Marathon bombings and asked for public help in identifying them.

The agency made the images public on Thursday and described the suspects “armed and extremely dangerous. " " No one should approach them. No one should attempt to apprehend them except law enforcement, " Special Agent Rick DesLauriers, the head of the FBI ' s Boston office, said at a press conference. The images show two men, one wearing a dark - colored baseball cap and the other a white cap, walking together near the finish line of Monday ' s marathon where two bomb explosions killed three people and injured 176 others. In a video apparently from a surveillance camera and shown by the FBI, the suspect in the white cap is seen putting his backpack down at the site of the second explosion within minutes of the blast. " Somebody out there knows these individuals as friends, neighbors, co - workers or family members of the suspects, " DesLauriers said, adding " though it may be difficult, the nation is counting on those with information to come forward and provide it to us. " The new images, the first major break in the feverish investigation, were released on the same day President Barack Obama traveled to Boston to console the city in the wake of the attack. At a special service at Boston ' s Cathedral of the Holy Cross, Obama said the perpetrators of the attack would be found and brought to justice.

" Yes, we will find you, and yes, you will face justice, " Obama told a congregation of 2,000 including relatives of the dead, survivors of the blasts, rescuers and city leaders.

" If they sought to intimidate us, to terrorize us, " the US president said, adding, " it should be pretty clear by now that they picked the wrong city to do it. " The FBI said it had no details of the identities or origin of the two men, but Deslauriers said the pictures will be distributed internationally. No one has claimed responsibility for the attack.