A mass execution of 47 men carried out by Saudi Arabia on Saturday prompted protests in Iran and condemnation from international human rights groups. The mass execution has been criticized as an act of political oppression.

Following the execution, protesters ransacked the Saudi Embassy in Tehran, Iran and set parts of the building on fire, CNN reported.

A prominent Shiite cleric, Sheikh Nimr al-Nimr, was among those executed on terrorism-related charges. Nimr had been an outspoken critic of the government and the Saudi royal family, CNN reported. He was arrested in 2012 and convicted of inciting sectarian strife and sedition, among other charges.

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In response to the execution, which occurred at 12 different sites throughout Saudi Arabia, Iran summoned the Saudi ambassador in Tehran to condemn the action. Iran, a Shiite-majority nation, is Saudi Arabia's regional rival, and it issued a statement warning the country that it "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," Iran's Foreign Ministry spokesman Hossein Jaberi said.

The human rights organization Amnesty International described the charges against Nimr as vague, and it denounced the death sentence, arguing that the case was part of an ongoing effort by Saudi Arabia, a Sunni-majority nation, to silence Shiite dissenters. The concerns raised by Amnesty International were echoed by the U.S. State Department, which urged the country to respect human rights and allow for peaceful protests.

"We are particularly concerned that the execution of [al-Nimr] risks exacerbating sectarian tensions at a time when they urgently need to be reduced," State Department spokesperson John Kirby said in a statement.

Saudi Arabia soundly rejected criticism of the mass execution, claiming that the 47 men killed were believers in extremist ideology and members of terrorist groups, including Al Qaeda, which had plotted and carried out terrorist attacks against civilians. The last time the country carried out an execution of this scale was in 1980, when 63 alleged jihadists were killed after seizing the Grand Mosque in Mecca.

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"The executions of at least 157 people in 2015, a year that began with the inauguration of a new monarch, King Salman, were a sharp increase from the 90 people put to death in 2014," The New York Times reported. "Saudi officials have said that the increase reflects a backlog of death sentences that had built up in the final years of the previous monarch, King Abdullah."