Raul Ruidiaz netted a hat-trick as Jose del Solar's Universitario came from behind to crush Los Caimanes 4-2, while second-half goals from Bernardo Cuesta and Minzun Quina inspired Melgar to a 2-0 victory over Union Comercio.
Universitario and Melgar are locked on 10 points and the same goal difference (+6) after four games, to sit three clear of the chasing pack.
Winless Los Caimanes made a dream start to proceedings in front of their home support at the Estadio Elias Aguirre when defender Ricardo Ronceros opened the scoring in the fifth minute.
That is as good as it got for the home side as Universitario scored two quick-fire goals before the half-time break courtesy of Ruidiaz's 15th-minute penalty and Carlos Olascuaga's effort two minutes later.
Ruidiaz completed his treble in the second-half with goals in the 48th and 63rd minute, while Edson Aubert pulled a goal back for Los Caimanes approaching the 70th-minute mark.
Universitario played the final five minutes with 10 men following Edwin Gomez's red card but it did not impact the scoreboard.
At the Estadio del IPD, Melgar flexed their muscles in the second-half to upstage Union Comercio.
After a scoreless opening half, the visitors finally made the breakthrough thanks to Argentina attacker Cuesta, who fired the ball into the roof of the net from close range in the 48th minute.
And Melgar put the result beyond doubt on the hour-mark when midfielder Quina curled a free-kick past Union Comercio goalkeeper Ronald Ruiz.
The result left Union Comercio in fourth (+3) place on seven points, adrift of Cesar Vallejo (+4) on goal difference after Franco Navarro's side accounted for lowly UTC Cajamarca 3-0 on Saturday.
Inti Gas (+1) and Juan Aurich (+0) are also level on seven points after both teams stumbled over the weekend.
Sporting Cristal beat Inti Gas 3-0 for their first win of the season on Saturday, while Juan Aurich played out a goalless draw at Alianza Lima - who had Julio Landauri sent off on the hour mark - on Sunday.
In other results, Universidad San Martin climbed up to seventh position after overcoming Sport Huancayo 4-2 on Sunday.
Cienciano ended a two-game losing streak with a routine 2-0 win at home to 10-man Real Garcilaso, who had Erick Coavoy sent off late in the game on Saturday.
Meanwhile, Guillermo Tomasevich scored twice as Leon de Huanuco routed San Simon 4-0 on Friday.