RIO DE JANEIRO, May 24 (Xinhua) -- A stunning long-range strike from forward Luan gave Gremio a 1-0 victory over Uruguay's Defensor Sporting and guaranteed the Brazilian side the top spot in their Copa Libertadores group.

Luan drilled a low 25-yard shot into the bottom corner just after the hour mark at Arena Gremio in the southern Brazilian city of Porto Alegre on Wednesday.

The result meant the defending champions finished top of Group A with 14 points, a point ahead of Paraguay's Cerro Porteno, who defeated Venezuela's Monagas 3-2 earlier in the day.

Meanwhile, Argentine giants River Plate were held to a goalless draw by Flamengo in Buenos Aires. Both sides progressed to the knockout phase by occupying the top two spots in Group D.

In Wednesday's only other match, Colombia's Santa Fe beat Emelec 3-0 in the Ecuadorian port city of Guayaquil. The result had no bearing on the Group D standings and both teams were eliminated from the tournament.