Players from both teams had to be separated in the tunnel at halftime after Liverpool forward Luis Suarez refused to shake United defender Patrice Evra's hand before kickoff. Suarez was making his first start since serving an eight-match ban for racially abusing Evra in October.
Police and stewards had to shepherd the players into their dressing rooms at halftime after an altercation ensued when Evra tried to confront Suarez.
When the second half started, Rooney scored twice in the opening four minutes to place United firmly in control.
Suarez scored a consolation goal in the 80th minute.