U.S. citizens abroad were also warned of potential reprisals, the department said shortly after U.S. President Barack Obama announced late Sunday the mastermind of the most devastating terrorist attack on U.S. soil and the most hunted man in the world had been killed in a firefight with U.S. forces in Pakistan.
Bin Laden's killing by U.S. forces created an "enhanced potential for anti-American violence, given recent counterterrorism activity in Pakistan," the State Department said.
Americans living or traveling abroad, particularly in areas previously hit by anti-American violence, should limit travel outside their homes and avoid large gatherings, it said.
Bin Laden ally the Taliban, the Sunni Islamist militia group that fled to Pakistan from Afghanistan in 2001 after being ousted by a U.S.-led invasion, Monday threatened joint Taliban and al-Qaida anti-U.S. retaliation for bin Laden's death.
"Taliban fighters have an admiration for Osama. It will affect their morale and will trigger the violence," a Taliban commander in eastern Afghanistan's Paktia province told The Wall Street Journal in a phone interview. "Taliban and al-Qaida fighters will start an offensive for revenge, and it will be a bloody offensive."
On the other hand, it is possible bin Laden's killing could undermine al-Qaida's attractiveness as a Taliban ally, U.S. and Afghan officials said, telling the newspaper his death could make it possible to negotiate a political solution.
"Without al-Qaida, we could deal with the Taliban. They would be just another party in another Third World country's civil war," a U.S. official told the newspaper before the news of bin Laden's death.
Former Pakistani army Gen. Talat Masood said he considered bin Laden's death "a huge setback for al-Qaida forces, in psychological and military terms."
"They'd built a myth surrounding him," he told the Journal. "He's a leader who is supposed to be irreplaceable."
He added, "It would have a good impact on Pakistan-U.S. relations."
Afghan government officials cheered the news of bin Laden's killing.
"Without Osama, and what he represents -- the only man to take down the U.S. -- young Muslims may not be as enthusiastic to join terrorist networks," Nasrullah Stanekzai, Afghan President Hamid Karzai's legal adviser, told the Journal.
It's also a big blow for the Taliban, he added. "This will hurt the Taliban's morale, but it won't stop their increased attacks on NATO and American forces," he said.