The Times of London said it had learned the three had attended lectures by Hamza at his North London mosque, where he taught that Muslims were obliged to kill non-believers to defend Islam.
The link between Hamza, 47, and the bombers, who killed 52 people and themselves, raises a possible explanation for the timing of the attacks.
On the morning of July 7, Hamza made his first court appearance on charge of inciting violence, but his case was postponed for six months. Later that day, the bombers struck.
His trial resumed last month and ended last week when a jury of seven men and five women returned unanimous guilty verdicts on 11 of 15 charges.
The cleric was sentenced to seven years in prison. The newspaper said Hamza is likely to be extradited to the United States where he faces terror charges, including conspiracy to take hostages.
Swim Week Miami Beach 2014 [PHOTOS]