Japan's Foreign Ministry issued a travel alert on Monday for Japanese nationals living or travelling in Europe, warning of "possible terrorist attacks" by al-Qaeda and affiliated groups.
The warning followed an alert from Washington to Americans, which said attackers may use "a variety of means and weapons and target both official and private interests" in Europe.
France and Britain immediately voiced support for the US security statement, which said "current information suggests that al-Qaeda and affiliated organisations continue to plan terrorist attacks."
The Japanese alert urges its citizens living or travelling in Europe to exercise full caution at possible attack targets, such as government and police facilities, public transport systems and tourist spots.
The US alert - which the State Department issued regarding specific events, and is one step down from a full travel warning - followed intelligence reports that suggested an al-Qaeda attack could be imminent.
To sum up, if you are in Europe, stay alert.