Hundreds of protesters stormed the Swedish embassy in Baghdad in the early hours of Thursday morning and set it on fire, sources said.
They said no embassy staff had been harmed and declined to elaborate.
Swedish embassy officials in Baghdad did not immediately respond to requests for comment.
The protest was called by supporters of Shiite cleric Moqtada Al Sadr before an expected burning of the Quran at a demonstration in Sweden.
A past burning of the holy book in Sweden led to widespread protests and condemnation from Muslim-majority nations.
Videos posted by One Baghdad, a popular Telegram channel that supports Mr Al Sadr, showed people gathering around the embassy about 1am on Thursday and storming it about an hour later.
Later videos showed smoke rising from a building in the embassy complex.
The authenticity of the videos could not be independently verified.
It was not immediately clear if anyone was inside the embassy at the time of the storming.
A similar incident occurred at the embassy in June.