The Watan newspaper said today that the men were heading to work at the Scientific Research Center near the Syrian capital when they were attacked yesterday.
The newspaper says the four victims were Syrian nationals, and suggested al-Qaida-linked militants were responsible for the attack.
Rami Abdurrahman of the Syrian Observatory for Human Rights said five nuclear engineers were killed and that one of the men was an Iranian national.
The Britain-based Observatory closely monitors Syria's fighting through a network of activists on the ground.
