Gabon added a 0-0 draw with Tunisia to their opening win against Cameroon as they put themselves within touching distance of the African Nations Cup quarter-finals.
There was little between the two sides in this Group D encounter at the Nossa Senhora do Monte and a draw was a fair result.
Hocine Ragued found himself unmarked in the box after three minutes but could not deflect Souheil Dhaouadi's corner goalwards.
At the other end, Eric Mouloungui was similarly wayward with his header when he was presented with a great chance in the 18th minute.
The best chance of the half, though, fell to Tunisia striker Amine Chermiti when Bruno Ecuele Manga made a mess of his backpass.
Chermiti rounded goalkeeper Didier Ovono but could not find the target with the goal at his mercy.
Ovono's opposite number, Aymen Mathlouthi, was looking less than secure and needed two attempts to gather Pierre Aubameyang's shot after a good run down the right.
Ovono almost put his side in trouble on the hour mark when he spilt a low free-kick from Yassin Mikari, but Daniel Cousin hacked it clear.
And there was a touch of desperation creeping into Algeria's play when Issam Jemaa flung himself to the ground under pressure from Moise Apanga.
Referee Codja Koffi was unsympathetic.
And Jemaa should have done better after 77 minutes when he stretched to meet a low cross from Dhaouadhi but could not make proper contact.
Tunisia substitute Ahmed Akaichi hit the bar in the 81st minute from close range, although the offside flag was wrongly raised anyway.
For Gabon, Aubameyang's touch let him down when he was played through by Cousin, who himself headed wide late on, but neither side could find a winner which would have been barely deserved.