(CNN) -- The mastermind of the worst terrorist attack on American soil is dead, U.S. President Barack Obama announced late Sunday night, almost 10 years after the attacks that killed more than 3,000 people.
Osama bin Laden -- the longtime leader of al Qaeda -- was killed by U.S. forces in a mansion outside the Pakistani capital of Islamabad along with other family members, a senior U.S. official told CNN.
U.S. officials have taken custody of bin Laden's body, Obama said. No Americans were harmed in the operation, he added.
Up-to-the-minute updates on bin Laden
U.S. diplomatic facilities around the world were placed on high alert following the announcement of bin Laden's death, a senior U.S. official said, and the U.S. State Department should be sending out a new "worldwide caution" for Americans shortly. Some fear al Qaeda supporters may try to retaliate against U.S. citizens or U.S. institutions.
Hundreds of people arrived at the White House late Sunday night and chanted, "USA! USA!" They then chanted, "Hey, hey, goodbye!" in reference to the demise of bin Laden and then spontaneously sang the national anthem.
Osama bin Laden, the face of terror
"This welcome news is a credit to our intelligence efforts and brings to justice the architect of the attacks on our country that killed nearly 3,000 people on September 11, 2001," said Sen. Susan Collins, R-Maine, the ranking Republican on the Homeland Security Committee, in a statement issued Sunday night.
The news brought some relief to the grieving family members of those killed on 9/11.
Celebrations in front of the White House
"This is important news for us, and for the world. It cannot ease our pain, or bring back our loved ones," Gordon Felt, president of Families of Flight 93, said in a statement. "It does bring a measure of comfort that the mastermind of the September 11th tragedy and the face of global terror can no longer spread his evil."