Hundreds of anti-riot personnel carriers set off for the city on Saturday to quell any potential protest on the part of its Shia population against the execution, according to Lebanon’s Al Ahd news website.
Security forces have also been alerted in other Shia-populated cities across Saudi Arabia.
The state-run Saudi Press Agency (SPA) reported Nimr’s execution, who was put to death alongside 46 others, earlier in the day, citing the kingdom’s Interior Ministry.
The ministry said those executed had been found guilty of involvement in “terrorism.”
Following the implementation of the cleric’s death sentence, all security outposts were evacuated across the country and all police stations shut down amid fears of Shia outrage.
An outspoken critic of Riyadh’s policies, Nimr was shot and arrested by the Saudi police in the Qatif region of the kingdom’s Shia-dominated Eastern Province in 2012.
He was charged with instigating unrest and undermining the kingdom’s security, making anti-government speeches, and defending political prisoners. He had rejected all the charges as baseless.
In 2014, a Saudi court sentenced the clergyman to death, provoking widespread global condemnations.
The sentence was upheld last March by the appeal court of Saudi Arabia. Back at the time, UK-based rights body Amnesty International called the sentence “appalling,” saying the verdict should be quashed since it was politically motivated.