By Simon Carraud and Sudip Kar-Gupta
PARIS (Reuters) - An assailant fatally stabbed a police officer inside the Paris police headquarters on Thursday then was shot dead by another policeman, a police union official said.
There was no word on the motive for the attack, which took took place in the heart of the French capital near Notre-Dame Cathedral.
The area around the police headquarters was sealed off and the nearest metro station was shut for security reasons, the transport authority said.
"As we speak, one colleague is dead following a knife attack. Another colleague is in a state of shock...and the person behind the attack has been shot by another colleague," Loic Travers, local head of the Alliance police union, said on BFM TV.
A police spokesman said he had no comment on the incident.
Police sources told Reuters the attacker was believed to have been a member of staff at the headquarters but there was no immediate confirmation of this.
(Writing by Benoit Van Overstraeten and Christian Lowe; Editing by Angus MacSwan)