The US Government has issued a warning to its citizens of a "continued threat" of terrorist attacks throughout Europe.
The Department of State urged US travellers to be "alert" to the possibility that extremists could conduct attacks with "little or no warning".
The advice, published on the department's website, cited recent incidents in France, Russia, Sweden, the UK, Spain and Finland as evidence of Isis's intent to conduct attacks throughout the continent.
"While local governments continue counter-terrorism operations, the Department remains concerned about the potential for future terrorist attacks," the statement said.
"US citizens should always be alert to the possibility that terrorist sympathisers or self-radicalised extremists may conduct attacks with little or no warning."
It listed several places deemed to be higher risk, such as tourist hotspots, transport hubs, markets, shopping centres and local government facilities.
"In addition, hotels, clubs, restaurants, places of worship, parks, high-profile events, educational institutions, airports, and other soft targets remain priority locations for possible attacks," it said.
US citizens should "exercise additional vigilance" in these locations, the statement added.
The updated guidance detailed a variety of tactics that could be used in any potential attack, including firearms, explosives, using vehicles as ramming devices, and sharp-edged weapons.
The advice reflects Isis' new favoured modus operandi of using vans, lorries and cars to plough into pedestrians, used in recent Isis-linked attacks in Barcelona, London, Nice, Berlin, Stockholm and Paris.
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