Leeds United and Millwall have condemned “vile” tragedy chants from the visiting fans during the Lions’ FA Cup victory at Elland Road.

Femi Azeez scored twice to send Millwall into the fifth round for the first time in six years but the match was overshadowed by events in the away end. Lions supporters were criticised by both clubs for referencing the murders of Leeds fans Christopher Loftus and Kevin Speight in 2000 in Istanbul before a Uefa Cup semi-final against Galatasaray.

“During today’s FA Cup fourth round tie with Millwall, we were extremely disappointed to hear vile chants relating to football tragedies from the away section at Elland Road,” a Leeds statement read. “We know the impact this has on the families of Christopher Loftus and Kevin Speight, along with the whole fan base of Leeds United. We will work with the police and Millwall Football Club to identify those involved, whilst we will also continue our efforts with the football authorities to help eradicate these chants from the game.”

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Winger Azeez netted a goal in each half against the much-changed Championship leaders, who saw Pascal Struijk’s penalty saved by the impressive Millwall goalkeeper Liam Roberts.

“We all have a duty to ensure Millwall Football Club is represented proudly and responsibly at all times,” Millwall said in a statement. “The club strongly condemns all forms of football tragedy abuse and is appalled to receive reports of such chanting from a minority at today’s Emirates FA Cup fixture against Leeds United.

“Both clubs have suffered tragic losses to their respective families in recent history. Chanting about this is entirely unacceptable and will not be tolerated by the club or the governing bodies. It has no place in football and the club will work closely with Leeds United and authorities to identify those responsible.”

Marcus Edwards needed fewer than 20 minutes to make an impact on his Burnley debut, scoring the winner as the Championship side knocked out Premier League Southampton, although few will call it an upset. The winger, on loan from Sporting, came off the bench and capitalised on defensive indecision to settle the match after a smart touch from Hannibal Mejbri as the struggling Saints failed to breach the Clarets, who kept their 23rd clean sheet of the season. “I was really pleased for Marcus and he’s someone we need to take care of now,” the Burnley manager, Scott Parker, said. “But I thought he was brilliant when he came on.”

Rodrigo Muniz scored either side of a fine Jonny Smith strike as Fulham avoided an upset against Wigan. Ronan Darcy thought he had sent the match into extra time when he put the ball into the back of the net in injury time, only to see the offside flag raised as the League One side were eliminated.

Extra time and penalties were required at the Bet365 Stadium where Stoke had come from two goals down, after Rubin Colwill and Yousef Salech set Cardiff on their way, to lead thanks to a Lewis Koumas double and Lewis Baker penalty, only to be pegged back by Colwill’s second of the match. After misses from Tatsuki Seko and Michael Rose, shining light Colwill scored the decisive penalty on a breathless afternoon in Staffordshire.

There was far less excitement at Deepdale where Preston and Wycombe went 120 minutes without a goal. Freddie Woodman saved spot-kicks from Daniel Udoh and Adam Reach in the shootout before Ched Evans sealed victory.