Gremio, Cerro Porteno and Junior kicked off their Copa Libertadores group campaigns with victories on Thursday.Brazilian club Gremio routed Bolivian outfit Oriente Petrolero 3-0. Douglas dos Santos scored a brace for the victors, with his goals sandwiched between Gilson's strike.Colombian side Junior secured a 2-1 away victory over Leon De Huanuco of Peru at the Estadio Heraclio Tapia Leon.John Viafara and Carlos Bacca netted for the victors, before Carlos Elias pulled a goal back in the 87th minute for the hosts, but it was not enough to earn the Peruvians a point.Paraguay club Cerro Porteno got off to a flying start with their 5-2 victory over Chilean side Colo Colo.Goals to Roberto Nanni and Julio Dos Santos had the hosts 2-0 ahead inside seven minutes at the Estadio General Pablo Rojas.The Chileans pulled one back six minutes later via Cristobal Jorquera, and the score remained 2-1 until the break.It took the hosts two minutes to regain their two-goal buffer when Juan Iturbe netted before Nanni scored a second, from the penalty spot, in the 69th minute.Esteban Paredes was on target for the visitors in the 74th minute, before Iturbe's second completed the goal fest in the 86th minute.Argentine side Godoy Cruz beat 10-man LDU Quito of Ecuador 2-1.Carlos Andres Sanchez opened the scoring for Godoy 16 minutes in at Estadio Malvinas Argentinas, before Neicer Reasco Yano leveled for LDU on 53 minutes.But Nicolas Sanchez struck just six minutes later the restore the lead for the hosts.The visitors finished with 10 men after Fernando Hidalgo Maldonado received a straight red card in the 90th minute.