WASHINGTON – “Justice has been done.”With those words, US President Barack Obama told the American public and the world Sunday night that the United States had succeeded in its 10-year mission to hold Osama bin Laden accountable for masterminding the September 11 attacks.RELATED:Lieberman praises US for bin Laden assassinationPhoto gallery: Revelers celebrate death of bin LadenJihadists: Bin Laden death will not mute Jihad call“Tonight, I can report to the American people and to the world that the United States has conducted an operation that killed Osama bin Laden,” Obama declared in a surprise television address from the White House.“For over two decades, bin Laden has been al Qaida’s leader and symbol, and has continued to plot attacks against our country and our friends and allies,” he said. “The death of bin Laden marks the most significant achievement to date in our nation’s effort to defeat al Qaida.”Earlier in the day, a small American team led a helicopter raid on a large compound in a residential area of Abbottabad, Pakistan, some 35 miles north of Islamabad, killing the Al Qaida leader in a fire fight and capturing his body, according to senior administration officials. The New York Times reported that his body was later buried at sea. No Americans were killed or injured, though a helicopter was lost to mechanical failure, they said.Obama stressed that bin Laden’s demise did not conclude America’s effort to end the threat posed by Al Qaida, and that future dangers remained. “There’s no doubt that al Qaida will continue to pursue attacks against us,” he warned. “We must –- and we will -- remain vigilant at home and abroad.”But he said that this moment would send a strong signal that the United States would do whatever was necessary to protect the American people.Obama also used the moment to appeal for national unity, recalling the bond that drew Americans together following the death of nearly 3,000 of their countrymen in the Twin Towers and Flight 93.“Tonight, let us think back to the sense of unity that prevailed on 9/11. I know that it has, at times, frayed,” he said. “Yet today’s achievement is a testament to the greatness of our country and the determination of the American people.” Already as Obama spoke, close to midnight, hundreds of tourists and local residents gathered at the White House to cheer his announcement, chanting “USA! USA!” and spontaneously belting out the Star Spangled Banner and other patriotic songs.Politicians on both sides of the aisle began releasing statements welcoming the development before the president had even made his official remarks.Obama spoke to former president George W. Bush, under whose tenure the September 11 attacks occurred, before addressing the American public. Bush later released a statement on the “momentous achievement.”He said that, "The fight against terror goes on, but tonight America has sent an unmistakable message: No matter how long it takes, justice will be done.”White House officials also reached out to foreign leaders before the officials announcement was released. Israel's ambassador the US Michael Oren was among those updated before Obama's statement. US military installations and embassies have been put on high alert and the State Department sent out an unusual world-wide travel warning for American citizens in anticipation that there could be revenge attacks.US authorities said they were not aware of any specific threats at this time, but according to the travel warning, US citizens traveling “in areas where recent events could cause anti-American violence are strongly urged to limit their travel outside of their homes and hotels and avoid mass gatherings and demonstrations.”In addition, local authorities are redoubling efforts to secure potential targets, including synagogues, across the country.