A fan group has condemned homophobic chanting as a “stain on our game” after four men were arrested on suspicion of offensive chanting during the FA Cup fourth round match between Hull City and Chelsea on Friday.

Spectators were warned over the PA system to stop discriminatory chanting late in the first half of the match at Hull City’s MKM Stadium, and that CCTV inside the ground was being monitored.

An on-screen message displayed inside the ground read: “There has been discriminatory chanting from fans inside the stadium. This is unacceptable and must cease immediately.”

A second-half update confirmed that action had been taken, including arrests.

Humberside Police confirmed to BBC Sport on Monday that three men – aged 24, 45 and 21 respectively – are under investigation pending further enquiries.

A second 21-year-old man was released without charge.

Officers also attended after reports that a steward had been assaulted. A 54-year-old man was arrested and enquiries are ongoing.

“We also received a further report of a second assault, where officers spoke to both parties involved to come to a community resolution,” a Humberside Police statement added.

“It is also believed a bottle was thrown on to the concourse during the match, and investigations remain ongoing.

“We continue to work in partnership with football clubs to ensure supporters and their families visiting the stadium, and the wider community, are safe whilst enjoying the football.”

It comes after Hull City reiterated in a statement on Thursday that “any chanting of a homophobic, racist or discriminatory nature is entirely unacceptable and will not be tolerated”.

The club added: “Any supporter found engaging in such behaviour will face serious consequences, including immediate ejection from the stadium, the possibility of a banning order, and potential criminal prosecution.”