The United States has warned Saudi Arabia, which has a Sunni Muslim majority, that its execution of a prominent Shia cleric behind anti-government protests "risks exacerbating sectarian tensions."
The US also urged Riyadh to "respect and protect" human rights, said State Department spokesman John Kirby, following the execution of Nimr al-Nimr.
Another 46 men were executed, including Shia activists and Sunnis accused of involvement in Al-Qaeda killings.
Among those executed was Adel bin Saad bin Jaza' Al-Dhubaiti, responsible for the murder of Irish BBC cameraman Simon Cumbers.
Mr Cumbers originally from Navan, Co Meath, was shot dead while filming a report about al-Qaeda in Saudi Arabia in 2004.
The executions sparked angry condemnation from Shia-majority Iran and Iraq, while the EU similarly expressed concern about possible "dangerous consequences" in a region already fraught with sectarian tensions.
Some of the executed were beheaded, while others were shot by firing squad.
"The United States also urges the government of Saudi Arabia to permit peaceful expression of dissent and to work together with all community leaders to defuse tensions in the wake of these executions," Mr Kirby said in a statement.
"We are particularly concerned that the execution of prominent Shia cleric and political activist Nimr al-Nimr 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."
Violent protests over executions
Angry crowds protesting at Saudi Arabia's execution of Nimr al-Nimr hurled petrol bombs and stormed the kingdom's embassy in Tehran Saturday before being cleared out by police, ISNA news agency reported.
In Mashhad, Iran's second biggest city, demonstrators meanwhile set fire to the Saudi consulate, according to news sites, carrying pictures of the alleged assault.
The incidents came hours after the announcement of the death of 56-year-old cleric Nimr al-Nimr, a key figure in anti-government protests in the kingdom since 2011.
The execution prompted strong condemnation from Shiite-majority Iran and Iraq.
"There are flames inside the embassy... demonstrators were able to get inside but have since been cleared out," ISNA said.
Protesters had been able to climb up onto the roof of the embassy before they were made to leave, it added.
