Facial recognition cameras have been installed at a train station in Berlin to help German intelligence services identify terrorists.
Germany has tightened security following a series of terror attacks in the past year.
Last summer, three attacks in the space of a week rocked the country. Ten people were killed and dozens more injured when lone wolves launched separate gun, bomb and machete attacks across Germany.
Several months later, a terrorist ploughed a lorry into people at a Christmas market in Berlin, killing 12 and injuring 48.
In a bid to crackdown on national terrorism, Germany has approved the installation of face-recognition cameras in Berlin.
The six-month surveillance project was launched at Berlin's Südkreuz station on Tuesday (2 August). Around 300 volunteers are taking part in the pilot.
The names and faces of people passing through the station will be saved in a database that is reviewed by police and the German interior ministry.
Many people are critical of the controversial security measure, claiming that it encroaches on German citizens' fundamental rights.
"We are heading towards a surveillance state that will give us less and less air," the President of the German Bar Association, Ulrich Schellenberg, told German media.
"There is no constitutional basis for implementing these methods extensively," he said.
Berlin's data security officer, Maja Smoltczyk, warned that the new technology carried "enormous risk of abuse" and said it threatened people's freedom of movement.
"Significant social control can be practiced on the people through the technology," she said.
But Germany's Interior Minister Thomas de Maizière defended the project, arguing that it would make people feel safer and help deter future attacks.
"Video surveillance makes an important contribution to police efforts as it serves as a deterrent against crime and helps them investigate offences," he said.