The blast hit a small bus carrying passengers in the Al-Zahraa neighborhood, which has repeatedly been targeted in bombings.
In December, four people were killed in a blast at a Red Crescent center in the neighborhood, and in February a double bomb attack claimed by the Daesh terrorist group killed 57 people.
Interviewed on state television, Homs governor Talal Barazi said four of those killed were female students heading to university on the bus, AFP reported.
Most of Homs is held by the government, with the exception of the Waer district, where the last phase of an evacuation is under way under a deal between the government and rebels.
Three waves of rebels and their families had already left Waer under an agreement first reached in December 2015, but subsequent evacuations stalled before a new deal was reached earlier this month.