Sweden terror alert: Brits told be vigilant

In updated travel advice, Britain's Foreign Ministry said Swedish authorities had successfully disrupted some planned attacks and made arrests.

"You should be vigilant at this time," it said, adding that "terrorists are very likely to try and carry out attacks in Sweden" with places visited by foreigners potential targets.

In a statement acknowledging Britain's changed travel advice, Sweden's National Security Advisor Henrik Landerholm reiterated the increased threats to Sweden since the burnings.

Landerholm said the storming of Sweden's embassy in Iraq on July 19, an attempted attack on its embassy in Lebanon on Aug. 9, and also the Aug. 1 shooting of an employee at a Swedish consulate in Turkey contributed to the risk assessment.

Quran burnings are permitted in Sweden under free speech rules, but Muslims see burning of their holy book as blasphemy.

The U.S. government has also warned of possible terrorist attacks in Sweden in its travel advice.