"The bodies of three people struck with bullets were taken to the hospital at Kram, close to Tunis, and 10 others have been brought to Charles Nicole hospital in Tunis," one source told AFP Friday.
The figure was confirmed by another medical worker who took part Friday in a major demonstration against Ben Ali in the city centre and was dispersed by police firing volleys of tear gas.
Two other people were reported killed in police fire in clashes in the central city of Kairouan late Thursday.
There was no official confirmation.
Ben Ali announced Thursday he had ordered police to stop firing on protesters as part of a host of measures to calm weeks of tensions, including a pledge to not seek another term after 2014.
"Enough firing of real bullets," he said. "I refuse to see new victims fall."
Ben Ali sacked his interior minister this week after widespread criticism of a harsh crackdown on the protests.
A Paris-based rights group said Wednesday it has the names of 66 people killed in the unrest, which erupted mid-December, a toll several times higher than one issue by the government of 21.