Image copyright Getty Images Image caption The first leg finished 1-1 after a late Gremio equaliser

Sixteen Flamengo fans have been arrested before Wednesday's second leg of their Copa Libertadores semi-final against Gremio in Rio de Janeiro.

Brazilian police targeted groups accused of "threats to kill police, rob and cause damage", who were planning to invade the Maracana Stadium.

Officials issued 27 warrants and 89 restraining orders.

"A gang was exchanging audio and video messages on social media to plan the invasion," Rio police said.

"Among the information gathered were threats to kill police, rob, cause damage and harass Gremio fans."

The sell-out game, poised at 1-1 after the first leg, sees hosts Flamengo aiming to reach the Copa Libertadores final for the first time since 1981.

In the other semi-final Argentina's River Plate start the second leg 2-0 up against hosts and rivals Boca Juniors at La Bombonera on Tuesday.