Witnesses are sought after a lit piece of paper was pushed through a letter box in Brighton, police said.
The fire was spotted at around 4.20am this morning (January 26), in a flat in St Peters Street.
Detective Sergeant Joe Jardine said: “Luckily the home owner woke up when he heard the smoke alarm and was able to quickly put the flames out without causing any injuries to himself.
“We are treating this as arson with intent and are investigating.
“We have not received any other reports of this nature.”
If you noticed anyone acting suspiciously in the area at this time, report it online or call 101 quoting reference 102 of 26/01.