The open-air Lycabettus Theatre in Athens was closed suddenly on Thursday, leading to the cancellation of two sold-out concerts by British singer James Blunt.

The ancient theatre was closed indefinitely by Athens Mayor Nikitas Kaklamanis for what were described as "security reasons."

There has been concern for months over the safety and repair of the stone bleachers in the Lycabettus Theatre, which is set in a hill overlooking Athens.

In early June, the Greek Tourism Development Agency ordered immediate suspension of the theatre to provide time for inspections and an in-depth technical study, as well as repairs.

Nonetheless, the closing of the theatre to the Blunt concerts Thursday and Friday caught organizers by surprise.

The Athens Festival, a separate agency that organizes concerts, complained that they had to return tickets to 6,000 people.

And Blunt's road crew say they were barred from accessing the theatre to remove concert equipment.