Microphones that will listen to street noise during the Olympic Games are being added to surveillance cameras around the city to improve security, Greece's public order minister said Thursday.

"If there is an explosion, we must be able to hear sound in real time. We can't wait for someone to make a phone call," Giorgos Floridis said.

The decision could add to protests against a giant surveillance system being installed around the capital. Several public demonstrations against Olympic security are being planned for this month.

In January, the mayor of an Athens suburb hosting the Olympic weightlifting event ordered municipal works to spray paint three cameras after residents complained about their right to privacy.

During the Olympics, stationary cameras around Athens will operate from 1,250 concrete columns 12 meters tall. Hundreds of cameras will also be installed at venues and other points around the city in addition to surveillance equipment on helicopters and a blimp.

Floridis insisted cameras will be vital for security during the Aug. 13-29 Games and flatly denied that the cone-shaped microphones will be used to monitor conversations or broadcast instructions to bystanders.