Adam LaRoche added to his home run tear with a two-run shot and the Washington Nationals beat the Chicago Cubs 9-2 in a fight-filled game Thursday night to finish a lopsided four-game sweep.

The trouble started with a testy exchange between Cubs bench coach Jamie Quirk and Nationals third base coach Bo Porter in the fifth inning. Quirk shouted from the dugout toward third base and Porter walked over to the railing, jawing and pointing his finger.

The benches and bullpens emptied, but there was no pushing or shoving. Quirk was ejected before play resumed.

In the sixth, Chicago reliever Lendy Castillo threw his first pitch of the inning near Bryce Harper's legs and the ball that sailed all the way to the backstop. Harper made a move toward the mound and was quickly intercepted by catcher Steve Clevenger.

Both teams spilled onto the field again, but this time things got a little nasty.

Players pushed and shoved each other in the infield and Clevenger took an open-handed swipe at Washington shortstop Ian Desmond, who accidentally knocked down first base umpire Bill Miller while backing away.

Clevenger, Cubs right-hander Manuel Corpas and Nationals lefty Michael Gonzalez were ejected — though neither pitcher was in the game. Order was finally restored and Washington went on to its fifth straight victory and eighth in nine games.

The Nationals (85-52), who have the best record in the majors, remained 7½ games ahead of second-place Atlanta in the NL East.

The Cubs (51-86) have lost 17 of their last 18 road games and six in a row overall. They were outscored 31-9 in the series.

Kurt Suzuki hit a three-run homer to help back Jordan Zimmerman (10-8), who struck out nine in seven innings. LaRoche hit his seventh home run in his last six games.

Washington tied a franchise record in each of the previous two games with six home runs.

Harper set the tone for the Nationals in the first inning Thursday, turning an apparent double into a triple and then sliding head first to score from third on a groundout.

Zimmerman, who allowed two earned runs and five hits, joined Gio Gonzalez and Stephen Strasburg as Washington pitchers with double-digit wins. Edwin Jackson and Ross Detwiler each have nine.

Harper also scored in the fourth inning, when he hit an infield single and came around from second on Ryan Zimmerman's two-out single.

Justin Germano (2-6) allowed seven hits and seven runs, six earned, in four innings — his shortest start of the season.

Anthony Rizzo homered in the first on a 3-0 pitch to give the Cubs their first lead of the series.

Chicago added another run in the second on triples by Starlin Castro and Darwin Barney.