Saudi Arabia said Saturday it had executed 47 people in a single day, including a dissident Shiite cleric, Nimr al-Nimr, who had repeatedly spoken out against the government and the Saudi royal family.

Nimr had been convicted of inciting sectarian strife, sedition and other charges following his 2012 arrest.

Iran, Saudi Arabia's regional rival, summoned the Saudi ambassador in Tehran to condemn the execution, the state-run IRNA news agency reported. The Shiite-majority nation issued a statement deploring the execution and warning that Saudi Arabia would pay a heavy price for its policies.

"The execution of a personality such as Sheikh Nimr who had no means other than speech to pursue his political and religious objectives only shows the depth of imprudence and irresponsibility," Press TV cited Foreign Ministry spokesman Hossein Jaberi as saying.

That prompted a rebuttal from Saudi Arabia, which "has summoned the Iranian ambassador to the Kingdom today and handed him a strong-worded protest note on the aggressive Iranian statements issued in response to the Islamic rulings carried out on terrorists in the Kingdom," state-run SPA news agency reported.

"During the meeting (in Riyadh), the (Foreign) Ministry expressed the Kingdom's denunciation and categorical rejection to such aggressive statements, which it considers a flagrant violation into the Kingdom's internal affairs," SPA said.

Loud and angry demonstrations broke out late Saturday at the Saudi Embassy in Tehran. Video showed at least one person tossing homemade firebombs at the embassy.

A CNN producer in Tehran said some protesters even made it in the building, set fire inside and ransacked some records. There were several arrests, police officers at the embassy told CNN.

There was some damage near the back of the embassy building, witnesses and a police officer said.

None of the Saudi diplomatic staff was in the embassy at the time.

When the CNN producer got to the scene, smoke was still coming from the building. As of 3 a.m. Sunday, the protest was waning and only a few hundred people and police officers in riot gear remained.