The attacks killed nearly 3,000 people in New York, at the Pentagon and aboard a hijacked airliner that went down in Pennsylvania.
At the White House, a few hundred people—political staff including National Security Advisor Susan Rice but also the White House chefs, gardeners and other residence staff—joined the Obamas for the ceremony.
In New York, police and relatives of those killed in the World Trade Center began the annual reading of the names of the victims at Ground Zero, now the site of the National 9/11 Memorial and Museum.
“Emotions and memories of 9/11 are with us so vividly today and always. We will #NeverForget our loved ones and first responders,” current New York mayor Bill de Blasio said on Twitter.
On Thursday, Federal Bureau of Investigation chief James Comey said there were “not any specific or credible threats” tied to the anniversary of the attacks, but that analysts were closely watching for threats from Al-Qaeda or the Islamic State.