Hotshot Gabriel Barbosa scored a brace as Flamengo hammered fellow Brazilians Gremio 5-0 on Wednesday to secure a place in the Copa Libertadores final against Argentine holders River Plate.

Bruno Henrique, Pablo Mari and Rodrigo Caio also got their names on the scoresheet as the Rio de Janeiro giants completed a 6-1 aggregate victory over the 2017 champions at the Maracana stadium.

River Plate made a 2-1 aggregate victory over their bitter Buenos Aires rivals Boca Juniors on Tuesday despite losing the second leg 1-0.

That was a repeat of last year's final, the second leg of which was controversially played in Madrid after the original fixture was twice postponed due to Boca players suffering cuts and smoke inhalation when their team bus came under attack from River fans.

This year's final will be played over a single match for the first time, on November 23 in Santiago.

Despite being Brazil's most popular team, Flamengo have only once before won the Copa Libertadores, back in 1981. River are looking for a fifth title.

Gremio fashioned the first clear chance of the match on 18 minutes when the livewire Everton -- one of the stars of Brazil's Copa America victory three months ago -- tricked his way into space inside the box and sent a cross into the danger area.

Diego Alves spilled it but from just six yards out and Maicon could only stab the ball back to the Flamengo goalkeeper.

From then on, though, the hosts dominated.

Rafinha, sporting rugby style head gear, chipped a cross in from deep on the right on 26 minutes and Henrique dashed across his day-dreaming marker before sending a diving header inches wide.

Ten minutes from half-time Uruguayan Giorgian de Arrascaeta tried to chip Gremio goalkeeper Paulo Victor who could only palm the ball out to Gabriel, but his speculative overhead bicycle kick bounced harmlessly across the face of goal.

The pressure told on 43 minutes, though, as Gabriel found space with a diagonal run and Victor could only palm his cross-shot into the path of Henrique, who had a tap-in.

A minute after half-time Flamengo doubled the lead as Brazil international Gabriel -- on loan from Inter Milan -- rifled high into the net from 15 yards after a poor clearing header from a corner.

The 23-year-old striker then held up a sign that read: "Today's there's a goal from Gabi Gol."

The tie was over as a contest 10 minutes later when Geromel was harshly adjudged to have brought down Henrique in the box.

Gabriel cooly slotted home the spot kick as Victor dived the wrong way, taking him top of the competition's scoring charts this season with seven goals.

A grinning Henrique, who had been carried off the pitch on a stretcher seemingly in agony, joined in the celebratory dance steps.

Mari and Caio got in on the act with headers from set pieces on 67 and 71 minutes as Gremio's defence capitulated.