The attackers also abducted another Lebanese, who is yet to be released.
The state Police Command, however, said it was a case of robbery, not kidnapping.
The spokesperson of the command, Mr Aminu Lawal, told newsmen on Tuesday in Kaduna that the police were interrogating the suspects to ascertain their involvement in the incident.
The deceased Padi Ibrahim, a Lebanese and a Nigerian, Aliyu Nuruddeen, both staff of Mother cat Construction Company, were killed around 7 a. m. while on their way to the Zaria Water Works site.
another Lebanese, Amir Drek, also a staffer of the construction company.
Eyewitnesses had said that the robbers blocked the road leading to the site and robbed passersby.
They said that when the victims sighted the gunmen, they made a U-turn to run for safety.
Meanwhile, Lawal said that the police were yet to find the missing Lebanese, Amir Drek.
“ We are trailing the suspects but we still strongly believe that it was robbery and not a kidnapping case. “