The executions -- typically carried out by public beheading -- bring to 114 the number this year, compared with 87 for all of 2014, according to AFP tallies.
"rights activists have raised concerns about the fairness of trials in the kingdom"
Ethiopians Argawi Aldo Heilan Meriam and Hadish Zel Alam had been convicted of killing countryman, the interior ministry said in a statement carried by the Saudi Press Agency.
"Under the conservative kingdom's “strict Islamic sharia legal code” (only executes in Saudi Arabia), many crimes are punishable by death."
They were put to death in the southwestern Jazan region, it said.
In a separate case, Pakistani Esmat Sharif, found guilty of smuggling heroin hidden in his body, was executed in Jeddah, the ministry said.
The fourth condemned man, Saudi Mushasha Harisi, was executed in Jazan after his conviction for shooting dead another Saudi in a dispute, the ministry said.
The number of Saudis and foreigners put to death so far in 2015 is up 131 percent on the figure for all of 2014, according to AFP tallies.
The file photo shows public beheading of a woman in Saudi Arabia.
"Saudi authorities have been on a campaign of death this year," Sarah Leah Whitson, Middle East and North Africa director of Human Rights Watch, said in June when the number of executions had already exceeded last year's total.
Under the conservative kingdom's “strict Islamic sharia legal code” (only executes in Saudi Arabia), many crimes are punishable by death.
"Saudi authorities have been on a campaign of death this year," Sarah Leah Whitson, Middle East and North Africa director of Human Rights Watch, said"
The interior ministry has cited deterrence as a reason for the punishments, but rights activists have raised concerns about the fairness of trials in the kingdom.
Amnesty International says Saudi Arabia is one of the world's most prolific executioners, along with China.
London-based Amnesty said the kingdom carried out a record 192 executions in 1995.