Rioting broke out around 9:30 AM (0930 GMT) in several suburbs including Simbaya and Hamadallaye, and angry protests continued as at least eight youths were treated for gunshot wounds.
The opposition had called for demonstrations in all parts of the capital against the ongoing lack of security which it blames on Conde's government.
"There were violent clashes between young protesters and police in Hamdallaye, where security forces shot three young protesters," a hospital doctor said on condition of anonymity.
"He was quickly rescued by his comrades," a policeman told AFP.
The gunfire continued into the afternoon as youths rallied in the streets, according to an AFP correspondent who witnessed panicked residents trying to get home.
Four other protesters were wounded in the northeastern suburb of Simbaya, witnesses and a police officer told AFP on condition of anonymity.
Guinea's opposition boycotted parliament in March in protest over the timetable for a presidential election, accusing Conde of using the Ebola epidemic as an excuse to postpone voting.
