The security warning was recently published on the American Embassy in Stockholm website.

The reason is possible revenge attacks in the wake of the Koran burnings that resulted in protests in several countries.

"US citizens are advised to exercise caution when in public places frequented by large numbers of people," it says, among other things.

Security police spokesperson Adam Samara says they have noted the information.

- As far as our assessment is concerned, the terrorist threat level is currently unchanged and remains at an elevated level.

At the same time, Säpo is following developments closely following recent events.

- It is a problematic situation that can be threatening, says Adam Samara.

"Keep a low profile"

Five points on the US Embassy website list actions their citizens should take:

• Avoid public gatherings.

• Keep a low profile.

• Be aware of your surroundings.

• Follow local media for updates.

• Check the embassy's website for the latest alerts and notices for US citizens.

The terrorist threat level in Sweden is assessed to be level three out of five, which means an elevated threat situation and that an attack may take place.

The assessment has been valid since 2010 with the exception of a period from November 2015 to March 2016 when the threat level was raised to a four.

SVT is looking for the American Embassy in Stockholm and the Swedish Foreign Ministry.

The text is updated.