The blast is said to have occurred at 7 a.m. local time (2:30 GMT) in Kabul's ninth district. Siawash is said to have been working at Da Afghanistan Bank and a magnetic bomb was placed on a Da Afghanistan Bank car.
Initially, four more fatalities were reported but it was later specified that two people had been killed, including Siawash, while two others were injured. So far, no organisation has claimed responsibility for the attack.
Heavy fighting is taking place across the Central Asian country, as the Afghan government and the Taliban remain locked in peace talks in the Qatari capital of Doha, with both sides expressing plans to conclude a long-lasting ceasefire.
The peace talks came after a February agreement signed by the United States and the Taliban in Doha, stipulating a gradual withdrawal of US troops as well as the beginning of intra-Afghan negotiations.