Last updated on .From the section Championship

Middlesbrough striker Britt Assombalonga has scored 15 goals in 43 league appearances this season

Middlesbrough secured their place in the play-offs with a win that all but ends Millwall's own promotion hopes.

Britt Assombalonga showed good composure to fire the hosts in front before the break.

A defensive mix-up between Lions goalkeeper Jordan Archer and defender Jake Cooper allowed Jonny Howson to tap in a second.

Defeat means Millwall's top-six hopes now rely on them beating Aston Villa and Preston and Derby not winning.

The game was marred at full-time when dozens of home supporters ran onto the pitch and started goading Millwall fans in the away end.

Plastic bottles were thrown by both sets of fans and it took about 10 minutes for police to restore order as the two groups tried to get at each other.

Some Middlesbrough fans ran towards the away section at full-time

The match itself saw few clear-cut chances at either end, with Millwall failing to truly test home goalkeeper Darren Randolph, while Mo Besic had a strong penalty claim for Boro late on.

Neil Harris' Lions have now only picked up one point from their past three games, with their tough end to the season against their play-off rivals proving decisive.

The loss at the Riverside Stadium followed a home defeat by Fulham and draw with Sheffield United.

Middlesbrough, meanwhile, look likely to face Aston Villa in the play-off semi-finals.