Lionel Messi became the first player to score in 15 consecutive Champions League seasons as Barcelona claimed a narrow win at Slavia Prague.Captain Messi gave Barca an early lead with a first-time finish after an exchange of passes with Arthur.The Czech champions were deservedly level when Jan Boril poked home Lukas Masopust's pass from 16 yards.But Messi's free-kick found Luis Suarez at the back post - and his cross-shot hit went in off Peter Olayinka.Barcelona, who are top of La Liga, have now won six consecutive games in all competitions.The result keeps Ernesto Valverde's side top of Group F on seven points from three games, three points above Inter Milan and Borussia Dortmund.Those two sides met at the San Siro in the group's other game, with Inter winning 2-0. Lautaro Martinez scored and had a penalty saved before Antonio Candreva's late clinching goal.Alex Oxlade-Chamberlain scored twice, including a stunning outside-of-the-boot finish, as Champions League holders Liverpool hammered Genk in Belgium.The Reds' 100% winning start to the Premier League ended with a draw at Manchester United on Sunday, but they returned to winning ways by showing their class in the Group E match.England international Oxlade-Chamberlain, who missed almost all of last season with a knee injury, drilled in a low shot in the second minute and brilliantly converted a second with a cool, first-time finish from Roberto Firmino's pass.Sadio Mane dinked in the third from Mohamed Salah's through ball and the Egyptian turned past a defender and rolled home the fourth late on.In other games, Chelsea won at Ajax, Leipzig beat Zenit 2-1 Napoli secured a 3-2 away victory against Salzburg, Lille drew 1-1 with Valencia and Benfica beat Lyon 2-1 at home