Police cordoned off the Champs Elysees street in Paris, April 20, 2017. (Xinhua/Chen Yichen)

PARIS, April 20 (Xinhua) -- One policeman was killed, and another severely injured in a shooting incident Thursday evening near the Champs Elysees shopping street in Paris.

At least two gunmen were involved in the shooting, and one was shot dead, local media quoted police source as saying.

Helicopters are seen patrolling the area, according to sources near the site.

Around 20 gunshots were fired around 8 p.m. local time, while shoppers were trapped in the stores, a source at the site told Xinhua.

The Paris police department has advised people to avoid going to the area on its Twitter account.

The cause of the incident remains unknown, but media reports say that the police are investigating it as a possible terrorist act.