A recent mass execution in Saudi Arabia has spurred international backlash, drawing condemnations from human rights advocates and United States officials while reportedly driving a wedge in diplomatic relations between the kingdom and other Islamic nations.

The state-run Saudi Press Agency reported that the country had killed 47 people that had been convicted of “terrorist crimes” on Saturday. Among them, according to the report, was Nimr al-Nimr, who the U.S. State Department characterized as an important leader in the Islamic community. His reported execution drew immediate rebuke from Amnesty International, one of the most vocal critics of the death penalty and Saudi Arabia’s seemingly unrelenting use of it.

“Saudi Arabia’s authorities have indicated that the executions were carried out to fight terror and safeguard security.” Philip Luther, the director of Amnesty’s Middle East and North Africa program, said in a statement. “However, the killing of Sheikh Nimr al-Nimr in particular suggests they are also using the death penalty in the name of counter-terror to settle scores and crush dissidents.”

Most of Saudi Arabia aligns with Sunni Islam, a branch that has different teachings than Shia Islam, creating some religious tension. Nimr was a leader in the Shiite minority, Amnesty said.

The group indicated Nimr had criticized Saudi Arabia’s government and was originally arrested for political protests in a traditionally Shiite region in 2011. Amnesty called his trial “political and grossly unfair,” and Luther said executing Nimr and 46 others when there were doubts about the fairness of the country’s criminal proceedings “a monstrous and irreversible injustice.”

It’s not the first time Amnesty has criticized Saudi Arabia’s executions. The group has previously said Saudi Arabia killed at least 151 people in the first 11 months of 2015, its highest such total in 20 years, and Amnesty isn’t alone in speaking out against the country’s use of the death penalty.

“We have previously expressed our concerns about the legal process in Saudi Arabia and have frequently raised these concerns at high levels of the Saudi Government,” State Department spokesman John Kirby said in a statement released Saturday. “We reaffirm our calls on the Government of Saudi Arabia to respect and protect human rights, and to ensure fair and transparent judicial proceedings in all cases.”

Kirby said the United States was “particularly concerned” about the death of Nimr.

In the statement, Kirby said the religious leader’s execution “risks exacerbating sectarian tensions at a time when they urgently need to be reduced. In this context, we reiterate the need for leaders throughout the region to redouble efforts aimed at de-escalating regional tensions.”

But those calls appeared to be falling on deaf ears.

CNN reported a group of protesters in Iran, which predominantly follows Shia Islam, waged an attack against the Saudi Arabian embassy following the execution. That attack led to Saudi Arabia and three other Muslim nations taking diplomatic actions against Iran, CNN reported.

On Monday, Kirby told a news briefing that the State Department condemned the attack on the embassy and encouraged the countries continue to seek diplomatic solutions to the conflicts.

“We continue to believe that diplomatic engagement and direct conversations are essential to work through differences,” Kirby told reporters. “Increased friction runs counter to the interests of all those in the international community who support moderation, peace and stability.”