In a Monday statement, the rights group said Saudi authorities, on average, have put to death one person every other day in 2015.
The number shows a dramatic 68-percent rise in comparison with 90 executions carried out over the whole of the last year.
The last time Riyadh executed over 150 people in a single year was in 1995, when 192 executions were recorded, according to the statement.
“The Saudi Arabian authorities appear intent on continuing a bloody execution spree which has seen at least 151 people put to death so far this year,” said James Lynch, Amnesty International’s deputy director for the Middle East and North Africa Program.
The statement also noted that nearly half of this year’s executions were for offenses that do not meet the threshold of “most serious crimes” for which the death penalty can be given under international human rights law.
“Under international human rights standards, most serious crimes are crimes that involve intentional killing,” it said.
Under the Saudi law, apostasy, armed robbery, drug trafficking, rape and murder carry the death penalty. Most Saudi executions are carried out by beheading with a sword.
According to Amnesty, 71 foreign nationals were among those executed in Saudi Arabia this year.
“Foreign nationals, mostly migrant workers from developing countries, are particularly vulnerable as they typically lack knowledge of Arabic and are denied adequate translation during their trials,” the UK-based human rights group said.
Riyadh has been under fire for having one of the world’s highest execution rates.
Earlier this year, Amnesty said in a report that court proceedings in Saudi Arabia “fall far short” of global norms of fairness.