The Philadelphia Union roared back with three second-half goals on Saturday to beat reigning champions Atlanta 3-1 in a battle for first place in Major League Soccer's Eastern Conference.

Kacper Przybylko rifled in the go-ahead goal in the 86th minute from a pass from second-half substitute Sergio Santos.

Santos put it out of reach with a goal two minutes later.

Philadelphia had knotted the score at 1-1 in the 66th when 18-year-old Brenden Aaronson scored his second goal in as many games.

Aaronson was set up by a ball from Haris Medunjanin.

Atlanta, coming off a victory over Minnesota United in the US Open Cup final on Tuesday, had gained the upper hand in first-half injury time as Josef Martinez scored -- the Venezuelan stretching his record with a goal in a 13th straight MLS contest.

Martinez missed an open net in the 80th minute and gave Atlanta fans a scare when he crumpled to the pitch in pain. But he was up quickly and back in the game.

With the victory, Philadelphia took sole possession of first place in the Eastern Conference with 51 points -- three more than Atlanta.

Elsewhere in the East, Ola Kamara scored twice in the first half to help DC United to a needed 3-0 victory over the Montreal Impact.

Kamara now has three goals in three appearances since returning from the Chinese Super League to MLS at the close of the secondary transfer window.

Paul Arriola also scored before halftime as DC halted a three-match losing streak despite the absence of suspended Wayne Rooney.

DC moved back in front of the New York Red Bulls into fourth place in the East while Montreal slipped out of the top-seven playoff positions.

In the West, FC Dallas maintained seventh spot with a 3-1 victory over FC Cincinnati -- a result that saw expansion club Cincinnati's playoff hopes officially ended.

Ryan Hollingshead, Michael Barrios and Zdenek Ondrasek scored for Dallas before Emmanuel Ledesma converted a penalty for Cincinnati.