Protestors gathered in front of the residence of British Prime Minister David Cameron to call on London to pressure Riyadh into revoking the death sentence of the Saudi opposition leader.
Carrying the photos of Sheikh Nimr, the demonstrators chanted anti-Saudi slogans and called for immediate and unconditional freedom of the jailed cleric, Al-Alam Arabic language news network reported.
They also condemned the Saudi regime’s policy of repression and emphasized the ineffectiveness of this policy and intimidation of dissent.
The sit-in came after unnamed European diplomatic sources last week said Saudi Arabia intends to carry out the death sentence of Sheikh Nimr.
Back in early 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. In October 2014, Sheikh Nimr's family reported that a Saudi judge has found him guilty of "sedition" and sentenced him to death.