Speaking to IQNA, Ayatollah Abbas Ka’abi, a member of Iran’s Assembly of Experts, said such a move will shake the foundations of Al Saud regime.
He underlined that regional nations ought to react to such a decision, adding that international and human rights organizations also have great responsibility in this regard.
His comments come as unnamed European diplomatic sources said Saudi Arabia intends to carry out the death sentence of Sheikh Nimr, who has been in detention for nearly three years on political charges.
According to the diplomats, Riyadh informed Washington of its decision to implement the death sentence of the opposition leader on Thursday, May 14.
Meanwhile, massive anti-Saudi rallies are planned to be held across the world on May 16 in support of Sheikh Nimr.
In March, a Saudi Arabian appeal court approved the death penalty of the prominent cleric.
Sheikh Nimr was detained in July 2012 following demonstrations that erupted in the country's Qatif region. He is accused of delivering anti-regime speeches and defending political prisoners.
His arrest sparked widespread protests in the Arab country.