Four policemen were stabbed to death Thursday in an incident inside the Paris police headquarters and carried out by a staff member at the headquarters, security sources said.

Investigators are investigating the possibility of a personal dispute, according to the same sources, where the bomber - who was killed in the courtyard of the building - works in the Intelligence Directorate at the headquarters.

The attack occurred in the afternoon at the main police station in the heart of the capital's historic center, near Notre Dame Cathedral.

Paris Mayor Ann Idalgou confirmed that "a number of people" had been wounded.

French media reported that French security forces closed the subway station and the area around the police headquarters.

A warning message was transmitted through loudspeakers at the Palais de Justice in Paris, opposite the police headquarters, declaring that "there had been an attack at the police headquarters" and that "the situation was under control" but at the same time indicated that the area was "still under surveillance".

Interior Minister Christophe Castaner postponed a planned visit to Turkey and went to the scene of the attack.