Embassies in Reykjavik have issued a warning to their citizens to exercise caution while moving about the Icelandic capital following a mass knife attack carried out a week ago.
Reykjavik police suspect gang conflict was behind an attack on November 17 when a group of 27 attacked three men with knives in a nightclub.
They warned that there were rumours of a revenge attack over the coming weekend.
The US embassy called on its citizens to avoid crowds and to keep an eye on the news media.
"If you observe unusual activity, you should leave the area immediately," it said.
The United Kingdom embassy put out a warning on Facebook.
"There has been some recent gang-related knife crime linked to nightclubs in the downtown area. Stay vigilant, take sensible precautions and avoid leaving valuables lying around," it said.
A spokesman for the German embassy said it was in close contact with the police and co-ordinating its response with them.