(CNN) -- The mastermind of the worst terrorist attacks on American soil is dead, U.S. President Barack Obama announced late Sunday night, almost 10 years after the attacks that killed about 3,000 people.

Osama bin Laden -- the founder and leader of al Qaeda -- was killed by U.S. forces Sunday in a mansion in Abbottabad, north of the Pakistani capital of Islamabad, along with other family members, a senior U.S. official told CNN.

In an address to the nation Sunday night, Obama called bin Laden's death "the most significant achievement to date in our nation's effort to defeat al Qaeda."

"Today, at my direction, the United States launched a targeted operation against that compound in Abbottabad, Pakistan," Obama said. "A small team of Americans carried out the operation with extraordinary courage and capability. No Americans were harmed. They took care to avoid civilian casualties. After a firefight, they killed Osama bin Laden and took custody of his body."

A congressional source familiar with the operation confirmed that bin Laden was shot in the head.

Footage that aired on CNN affiliate GEO TV on Monday showed fire and smoke spewing from the compound where bin Laden was killed.

Half a world away, the scene outside the White House was of pure jubilation.

Hundreds reveled through the night, chanting "USA! USA!" Others chanted "Hey, hey, hey, goodbye!" in reference to the demise of bin Laden. Many also spontaneously sang the national anthem.

The news also brought some relief to family members of those killed on 9/11.

"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."

"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.

Bin Laden eluded capture for years, once reportedly slipping out of a training camp in Afghanistan just hours before a barrage of U.S. cruise missiles destroyed it.

He had been implicated in a series of deadly, high-profile attacks that had grown in their intensity and success during the 1990s. They included a deadly firefight with U.S. soldiers in Somalia in October 1993, the bombings of two U.S. embassies in East Africa that killed 224 in August 1998, and an attack on the USS Cole that killed 17 sailors in October 2000.

In his speech, Obama reiterated that the United States is not at war with Islam.

"I've made clear, just as President Bush did shortly after 9/11, that our war is not against Islam. Bin Laden was not a Muslim leader; he was a mass murderer of Muslims."

The Council on American-Islamic Relations (CAIR), a Muslim civil rights and advocacy organization, released a statement Monday morning welcoming the death of bin Laden.

"As we have stated repeatedly since the 9/11 terror attacks, bin Laden never represented Muslims or Islam. In fact, in addition to the killing of thousands of Americans, he and al Qaeda caused the deaths of countless Muslims worldwide," the statement said. "We also reiterate President Obama's clear statement tonight that the United States is not at war with Islam."

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 issued a "worldwide caution" for Americans. The travel alert warned of the "enhanced potential for anti-American violence given recent counter-terrorism activity in Pakistan." Some fear al Qaeda supporters may try to retaliate against U.S. citizens or U.S. institutions.

But for now, many Americans were soaking up the historic moment.

"It's what the world needed," said Dustin Swensson, who recently served in Iraq and joined the revelers outside the White House. "(I'll) always remember where I was when the towers went down, and I'm always going to remember where I am now."

CNN's Ed Henry, Jeanne Meserve and Elise Labott contributed to this report