The demonstrators, supporters of firebrand Shiite Muslim leader Moqtada Sadr, entered the building and remained inside for about 15 minutes before leaving peacefully as security forces deployed, the photographer said.

The protesters first rallied outside the embassy in response to a call by Sadr who demanded the removal of the Swedish ambassador, echoing outrage in several Muslim countries over the Koran burning Wednesday in Stockholm.

The demonstrators also distributed leaflets that carried messages in Arabic and English that said: "Our constitution is the Koran. Our leader is Al-Sadr".

"Yes, yes to the Koran," was also scrawled on the gate leading to the embassy, according to the photographer.

Sadr's supporters also torched rainbow flags that represent the LGBTQ community, after the powerful cleric suggested this would be "the best way to provoke" those who back Koran burnings.

Stockholm's foreign ministry said in a statement it was "well informed about the situation. Our embassy staff are safe."

Salwan Momika, 37, who fled to Sweden from Iraq several years ago, stomped on the Koran before setting several pages alight in front of Stockholm's largest mosque.

He had been granted a special permit from the police for the protest in line with free-speech protections.

The Iraqi foreign ministry has said such acts would only "inflame" the feelings of Muslims around the world.