Ariel Rodriguez's brace and a Mauricio Castillo effort helped Deportivo Saprissa triumph at the Estadio Nacional de Costa Rica in San Jose.
Mario Camacho pulled a goal back for the visitors in the 81st minute but they were unable to stage a remarkable comeback.
Ronald Gonzalez Brenes' Saprissa side are two points clear at the top after winning their second game in three this league season.
Rodriguez struck in the 26th and 52nd minutes and Castillo's goal wrapped up the victory before Camacho's effort gave Carmelita some late joy.
Santos de Guapiles and Puntarenas played out a 1-1 draw after Eder Monguio cancelled out Daniel Colindres' 13th-minute opener.
Perez Zeledon and UCR remain winless after their entertaining 2-2 draw in San Isidro de El General.
UCR twice went ahead through Lucas Gomez and Jameson Scott, with the latter putting his side back in front after Jorge Gatgens' equaliser.
But Gomez was sent off in the 77th minute and Perez Zeledon took advantage of their numerical advantage with Henry Cooper netting the leveller.
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