River Plate hit three late goals to join Lanus on maximum points with a third win of the Clausura season at home to Tigre on Sunday.
The Buenos Aires-based side went behind to Alejandro Donatti's 55th-minute effort but were 3-2 winners after a remarkable run of three goals in the last four minutes.
Carlos Luna scored in the 86th and 87th minute before the side's traded last-gasp efforts from Juan Iturbe and Matias Perez Garcia in the closing seconds. Tigre also had Ruben Botta sent off in the final minute.
Godoy Cruz are a point clear in third as they remained unbeaten with a 2-1 win at Atletico Rafaela.
Leandro Grimi's 17th-minute goal and Mauro Obolo's penalty four minutes later were enough to render Diego Vera's late goal irrelevant.
Independiente scored in each half to see off Racing Club 2-0, with Leonel Miranda and Jonathan Santana on target. Diego Villar saw red late on for Racing.
Belgrano Cordoba won the remaining fixture 2-1 at home to Colon Santa Fe.
The scores were tied after Cesar Pereyra (40) and Emmanuel Gigliotti (57) notched, leaving Martin Zapata to win it a minute from time.