"Six bodies were retrieved and six injured people, including a pregnant woman, have been transferred to hospital at Bainem" west of the capital Algiers, private television channel Ennahar said.
The boat capsized around 4:00 am local time (0300 GMT), it added.
A search was ongoing for an unspecified number of missing people.
The boat's occupants originated from various sub-Saharan African countries. They were attempting to reach Europe.
More than 2,350 would-be migrants have been rescued or intercepted in the first seven months of this year off Algeria, according to data provided by national authorities.
Spain is a favoured destination for migrants embarking from the North African nation.