This came after Saudi Arabia executed Sheikh al-Nimr in defiance of international calls for the release of the prominent Shia cleric.
Lebanon's Supreme Islamic Shia Council called execution of cleric Nimr al-Nimr a "grave mistake".
Lebanese resistance movement Hezbolla has termed it an “assassination” and a "ugly crime." Hezbollah said Nimr had "demanded the squandered rights of an oppressed people". The resistance movement noted that Nimr resisted oppression with words.
Al-Nimr was a peaceful dissident who advocated greater rights for the kingdom's Shia Muslims.
A large number of of protesters in Saudi Arabia's Eastern Province marched through Nimr's home district of Qatif shouting "down with the Al Saud".
Several hundred gathered in nearby Bahrain to protest the killing and oppression.
Several media channels across the globe carried non-stop coverage of clerics.
Analysts and experts praised Nimr and predicted the downfall of Saudi Arabia's Sunni ruling family.
The Muslim leaders in Iraq, Kuwait, Lebanon, and Yemen also warned of reprisals.
Yemen's Houthi movement said Nimr had been given a "mock trial".
Hundreds of protesters demonstrated in the Muslim-majority northern province of Kashmir, where one protest organizer said the charges against Nimr were "baseless".
Reports indicate that Muslims have taken to the streets in protest across the Iranian capital Tehran
Several Iranian officials, including foreign ministry spokesman Hossein Jaber Ansari, accused the Al Saud of supporting terrorism.
"The Saudi government supports terrorists and takfiri extremists, while executing and suppressing critics inside the country," the foreign ministry spokesman said
Politicians and cleric in Iraq called on the government to sever ties with Saudi monarchy. This came just one day after Saudi Arabia reopened its embassy in the Iraqi capital Baghdad for the first time since 1990.
Clerics, officials and students across the globe have lashed out at the kingdom.
United Nations Secretary-General Ban Ki-moon has also been "deeply dismayed" over the execution.
Meanwhile, Germany's Foreign Ministry has said al-Nimr execution "strengthens our existing concerns
U.-based Human Rights Watch's Middle East director Sarah Leah has said that al-Nimr was convicted in an "unfair" trial and that his execution "is only adding to the existing sectarian discord and unrest.
Al-Nimr's brother said that the executions came as a "big shock" because "we thought the authorities could adopt a political approach to settle matters without bloodshed."
Saudi Arabia carries out most executions through beheading and has drawn comparisons to extremist groups like Daesh terrorist group — which also carry out public beheadings.