Jimmy Floyd Hasselbaink's side scored a first-half penalty through Damien McCrory and second half-goals from Stuart Beavon and Matt Palmer, while nearest rivals Shrewsbury lost at fellow promotion hopefuls Wycombe.
The 1-0 victory for Wycombe, courtesy of a first-minute goal from Sam Wood, moved the hosts up into second, while Shrewsbury slipped to third.
Southend sit fourth after a 3-1 win away to Dagenham and Redbridge, with the goals coming from Joe Piggot, Ryan Leonard and a Barry Corr penalty.
Dagenham had equalised in the first half through Ayo Obileye but the defeat leaves them in 18th in the table.
Elsewhere, an own goal by Mansfield Town’s Ryan Tafazolli after 21 minutes gave all three points to visitors Bury, who lie fifth.
Luton Town remain in the play-off places despite a 2-0 defeat at Portsmouth, who scored through Matt Tubbs and Ryan Taylor.
Plymouth Argyle’s 0-0 draw at Oxford United was enough to keep them in the promotion play-off picture, but only on goal difference from Stevenage, who drew 1-1 at Cambridge.
Bottom club Hartlepool’s survival hopes were boosted by an Andy Parrish own goal in the 1-0 away win against Morecambe, as fellow strugglers Tranmere Rovers went down 1-0 at Northampton thanks to a Ryan Cresswell goal.
Exeter were 3-2 winners over AFC Wimbledon and the game between York City and Carlisle United, with both teams looking to move away from the relegation battle, ended 0-0.
