The victory helped the defending champion maintain its lead with 24 points. Fanja's 2-0 win against Saham on Thursday kept it on close heels of the leader, as it trailed Arouba by just a point.
Despite the defeat to Arouba, Sohar was in third place with 21 points and it is followed by Dhofar, which played a goalless draw against hosts Al Khabourah to collect a point and collect 19 points.
Suwaiq, which was held to a 1-1 draw by Muscat on Friday, also has 19 points. Al Nasr's narrow 1-0 win over Musannah on Thursday helped it climb to sixth spot, a point ahead of former champion Al Nahda, which played out a goalless draw against Sur on the same day.
In another game on Thursday, Salalah, which is in the relegation zone, managed a 3-2 win over Al Shabab. The victory, however, failed to make much of a difference as it remained at the bottom of the table.
Standings (after 12th round): 1 Al Arouba (24 pts), 2 Fanja (23), 3 Sohar (21), 4 Dhofar (19), 5 Al Suwaiq (19), 6 Al Nasr (18), 7 Al Nahda (17), 8 Saham (16), 9 Al Musannah (15), 10 Al Khabourah (14), 11 Sur (9), 12 Al Shabab (9), 13 Muscat (8), 14 Salalah (6).