Reports have emerged of crowds breaking into and setting fires at the Saudi Arabian embassy in Tehran.
The Iranian police have dispersed the protesters from inside the embassy and the Iranian Foreign Ministry has appealed for calm, and to respect diplomatic premises, according to reports.
Photos and video posted to social media, which have not been verified, show numerous protesters within the embassy compound, and fires lighting up the building. One video appears to show a Molotov cocktail being thrown at the building.
An Iranian journalist seemingly at the scene, Sobhan Hassanvand, posted images of masked protesters clutching a Saudi flag which appears to have been torn down, and video of protesters trashing rooms.
The protests follow the Saudi execution of a highly regarded Shia Muslim cleric, Sheikh Nimr al-Nimr on Saturday.
The Iranian government itself has been highly critical of Nimr’s execution. “The Saudi government supports terrorist movements and takfiri [ideology],” Iranian Foreign Ministry spokeman Hossein Jaber Ansari stated, “but confronts domestic critics with oppression and execution... the Saudi government will pay a high price for following these policies.”
There have also been protests reported in the Saudi Arabia’s Eater Province, where local police were reportedly withdrawn and replaced by armoured units to maintain order.
There were small protests outside the Saudi embassy in London. Hilary Benn, shadow foreign secretary, tweeted: “Saudi Arabia profoundly wrong to execute Sheikh Nimr al-Nimr. Opposed to the death penalty and Amnesty had serious concerns about his trial.”
Protests were also reported in Yemen, Pakistan and Kahmir.
In Bahrain, which has a Shia majority and has long complained of persecution from Sunni Saudi Arabia, protests against the execution turned violent and saw police clash with protesters.
In Lebanon, Shia militant group Hezbollah denounced the execution as an “assassination” and the Lebanese Shia council called it a “grave mistake”.
In Iraq, there has been widespread condemnation. Moqtada al-Sadr, a powerful Shia leader who fought against the American occupation, called for "angry demonstrations” in protest.
Additional reporting by Reuters