An Egyptian bus driver for a private construction company has been arrested after allegedly shooting dead six employees of the firm and injuring up to 12 others while on the job in Cairo, a local news agency reported.

Mahmoud Taha Swellem, 46, opened fire with an automatic rifle on the employees on Tuesday after he stopped the bus in the middle of the highway while driving them to work for Egyptian consruction firm Arab Contractors, Mena reported.

The man was soon detained by police after the incident and is now under investigation.

But the report did not give a motive for the sudden assault.

There were women employees out of the 23 workers in the bus at the time of the attack but none were killed or injured, Mena said.

The media source added that the victims included a financial manager and a department head.

An official with the Arab Contractors confirmed the shooting but did not give details, saying a statement would be issued shortly.