Airports in the United States and Europe are on greater alert in the wake of al-Qaeda chief Osama bin Laden's death.
Britain, France and the US have warned of possible reprisal attacks from terrorist groups after US forces killed bin Laden in a raid on a compound on the edge of Abbottabad in Pakistan.
Bin Laden was found nine and a half years after he masterminded the September 11 attacks.
Travellers worldwide are to expect increased security at airports, and delays if they are travelling during this period.
America has issued a worldwide advisory to all US citizens travelling and living abroad about the potential for anti-American violence in the wake of the killing of bin Laden.
"Given the uncertainty and volatility of the current situation, US citizens 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," the advisory said.
US government facilities worldwide remain at a heightened state of alert, the State Department said, and some may temporarily close or suspend public services when necessary.
Americans abroad are urged to keep an eye on media coverage of local events and to maintain contact with the nearest US embassy or consulate, the advisory said.
Israeli Police have also raised alerts. Operations branch chief Commander Nissim Mor has ordered all districts to map out the locations of US buildings and homes of officials, prepare for possible disturbances, and increase patrols around US sites in the country.
