Officers were called at 11.11pm on Thursday to reports of an incident at King Kebab in Tempest Road, Beeston.
A man has been arrested on suspicion of wounding and was yesterday (June 9) in custody.
A West Yorkshire Police spokesperson said: “Officers attended and found a 56-year-old man with a serious knife injury to his arm.
“He is currently being treated in hospital. His injuries are not life threatening.
“A 23-year-old man was also assaulted during the incident and received minor injuries.
“A 34-year-old man has been arrested on suspicion of Section 18 wounding and is currently in custody. Other suspects have been identified and enquiries are ongoing to arrest them.”
Unconfirmed reports indicated that the victim of the attack could have been the shop owner.
It is understood that a video relating to the incident was posted onto social media.
People online commented on crime happening in the area.
Spike Thomas said: “Normal night in Beeston these days...”
And Rosie Meerun said: “A lot of crimes seem to happen on Tempest Road.”
Anyone who witnessed the incident or who has any information that could assist police with their investigation is asked to contact Leeds District CID via 101, quoting crime number 13170261004.
Alternatively, information can be passed on by calling the independent charity Crimestoppers anonymously on 0800 555 111.