Fire crews were called at 3am today (Sat Oct 29) after a settee was set on fire in the corridor of block two of the Poplar Mount flats in Bramley.
Two people who were unable to get out of one flat were rescued by firefighters.
Three men from other flats suffered smoke inhalation and were treated at the scene by paramedics.
One of the men who was hurt had tried to tackle the blaze, which was extinguished by fire crews.
A fourth man who suffered smoke inhalation was given oxygen at the scene by firefighters.
A West Yorkshire Police spokesman said: “Police were called to flats in Poplar Mount, Leeds at about 3.08am this morning to a report a fire had broken out in a hallway.
“The matter is being treated as an arson by police and enquiries to determine the cause are ongoing by Leeds District CID and fire service investigators.
“Anyone who has information about how the fire may have started is asked to contact Leeds District CID on 101 or the independent Crimestoppers charity on 0800 555 111.”
Fire crews used high powered fans to clear thick smoke from floors one to seven at the flats.
Pumps from Stanningley, Leeds and Hunslet attended the incident along with an aerial appliance from Leeds.