LISBON, Dec 2 (Reuters) - Porto moved five points clear in the Portuguese Premier League on Saturday with a 2-0 home win over neighbours Boavista ahead of next week's Champions League tie with Arsenal.

Porto top the standings with 31 points from 12 matches with Sporting, who were defeated by 2-0 by old rivals Benfica on Friday, second on 26.

The result takes Benfica into third place with 22 points, a morale-boosting victory before their decisive Champions League match at Manchester United.

Porto opened the scoring after 51 minutes through Ricardo Quaresma with a shot from outside the area surprising Boavista goalkeeper Karim.

Helder Postiga, the league's top scorer with nine goals, got the second after 74 minutes after a free-kick by midfielder Raul Meireles.