By Timour Azhari and Anna Ringstrom

BAGHDAD/STOCKHOLM (Reuters) -Hundreds of protesters stormed the Swedish embassy in Baghdad in the early hours of Thursday morning and set it on fire, a source familiar with the matter and a Reuters witness said, in a protest against the expected burning of a Koran in Sweden.

The source said no embassy staff had been harmed and declined to elaborate further. Swedish embassy officials in Baghdad did not immediately respond to requests for comment.

A Swedish foreign ministry spokesperson declined to comment.

Thursday's demonstration was called to protest the second planned Koran burning in Sweden in weeks by supporters of Shi'ite cleric Muqtada Sadr, according to posts in a popular Telegram group linked the influential cleric and other pro-Sadr media.

Swedish news agency TT reported on Wednesday that Swedish police granted an application for a public meeting outside the Iraqi embassy in Stockholm on Thursday.

The application says the applicant seeks to burn the Koran and the Iraqi flag, TT reported.

Two people were set to participate in the demonstration, according to TT, adding one of the people was the same person who set a Koran on fire outside a Stockholm mosque in June.

A series of videos posted to the Telegram group, One Baghdad, showed people gathering around the embassy around 1 a.m. on Thursday (2200 GMT on Wednesday) chanting pro-Sadr slogans and storming the embassy complex around an hour later.

"Yes, yes to the Koran," protesters chanted.

Videos later showed smoke rising from a building in the embassy complex. Reuters could not independently verify the authenticity of the videos.

It was not immediately clear if anyone was inside the embassy at the time of the storming.

Late last month, Sadr called for protests against Sweden and the expulsion of the Swedish ambassador after the Koran burning in Stockholm by an Iraqi man.

Swedish police charged the man with agitation against an ethnic or national group. In a newspaper interview, he described himself as an Iraqi refugee seeking to ban the Koran, the central religious text of Islam, believed by Muslims to be a revelation from God.

Two major protests took place outside of the Swedish embassy in Baghdad in the aftermath of that Koran burning, with protesters breaching the embassy grounds on one occasion.

The governments of several Muslim countries, including Iraq, Turkey, the United Arab Emirates, Jordan and Morocco issued protests about the incident, with Iraq seeking the man's extradition to face trial in the country.

The United States also condemned it, but added that Sweden's issuing of the permit supported freedom of expression and was not an endorsement of the action.

(Reporting by Timour Azhari; Additional reporting by Anna Ringstrom in Stockholm; Writing by Timour Azhari; Editing by Tom Hogue and Lincoln Feast)