Angry Iranian protesters stormed Saudi Arabia's embassy in Tehran in the early hours of Sunday, smashing furniture and starting fires before being removed by the police, Reuters reports.
The protesters gathered outside the embassy to protest against Saudi Arabia's execution of Nimr al-Nimr, a prominent cleric from the kingdom's Shiite minority, on terrorism charges that Iran said were unjustified.
They then broke into the building and lit fires inside before being cleared by police, the ISNA news agency reported.
Images shared on social media appeared to show protesters smashing furniture inside the embassy, according to Reuters.
Later images showed police in full riot gear guarding the premises as firefighters doused the building. ISNA said Tehran's police chief was on the scene to restore calm.
On Saturday, Iran's foreign ministry spokesman Hossein Jaber Ansari strongly condemned Riyadh for executing Nimr despite repeated Iranian requests for clemency.
"The Saudi government supports terrorist movements and extremists, but confronts domestic critics with oppression and execution… The Saudi government will pay a high price for following these policies," he said.
"The execution of a figure like Sheikh al-Nimr, who had no means to follow his political and religious goals but through speaking out, merely shows the extent of irresponsibility and imprudence."
Parliament speaker Ali Larijani also condemned Nimr's death, saying Riyadh would not emerge "easily from the quagmire they created by the martyrdom of this great sheikh."
Shiite Iran and Sunni Saudi Arabia are major rivals in the Middle East and are arrayed on opposing sides in several regional conflicts.
Nimr was a driving force of the protests that broke out in 2011 in Eastern Province, where the Shiite minority of Saudi Arabia complains of marginalization.
He was arrested in 2012, with the Interior Ministry describing him as an "instigator of sedition".
More than 20 Shiites were killed in protests between 2011 and 2013 in the Shiite district of Qatif, with three of them killed in protests in the two days after Nimr's arrest.
Saudi Arabia is notorious for its violations of human rights and specifically those of women, employing a religious police whose job is to enforce Islamic Sharia law.
One of the most notorious practices in Saudi Arabia is the ban on women driving, which has been targeted by a long-standing campaign which has urged women to defy the ban.
Yet despite its violation of human rights, Saudi Arabia recently has a seat on the UN Human Rights Council, being one of several countries with questionable human rights records to win seats in this body.
Saudi Arabia's envoy to the UNHRC was in September selected to head an influential panel on human rights, despite Riyadh's own poor track record for human rights issues.