The UK updated its travel advice for Sweden on Sunday, warning citizens who plan to visit the country of possible terrorist attacks following Quran burnings by anti-Islam activists that have outraged Muslims.
Swedish authorities had successfully disrupted some planned attacks and made arrests, the UK's Foreign Office said.
"You should be vigilant at this time," it said, adding that "terrorists are very likely to try to carry out attacks in Sweden" with places visited by foreigners potential targets.
In a statement acknowledging the UK's changed travel advice, Sweden's national security adviser Henrik Landerholm reiterated the increased threats to Sweden since the burnings.
Mr Landerholm said the storming of Sweden's embassy in Iraq on July 19, an attempted attack on its embassy in Lebanon on August 9, and also the August 1 shooting of an employee at a Swedish consulate in Turkey contributed to the risk assessment.
Protests against desecration of Quran in Sweden - in pictures
Quran burnings are permitted in Sweden under free speech rules, but Muslims see the burning of their holy book as blasphemy.
The US government has also warned of possible terrorist attacks in Sweden in its travel advice.