Breaking: Gunshots reported outside historic Notre Dame cathedral in Paris

Paris authorities placed the historic Notre Dame Cathedral on lockdown following reports that an attacker went after a police officer with a hammer Tuesday.

One social media user tweeted while he was "trapped" inside the landmark, as French officials were "not letting anyone in or out."

The BBC reported that a man tried to attack a police officer with a hammer. The attacker was then shot by the officer.

One man who said he had just visited Notre Dame moments before the attack tweeted that "shots were fired" and that "people ran everywhere."

CNN reported on air that Paris police were asking residents and tourists to avoid the area.

It was not immediately clear if the incident was terror-related.

No confirmation at this stage whether Notre Dame incident can be qualified as terrorism, according to police https://t.co/GSKO4E2aXL pic.twitter.com/01SnD3VxDA

— CBS News (@CBSNews) June 6, 2017

The news came as Paris is still on high alert from the November 2015 terror attack at the Bataclan theater, which killed around 130 people.

More recently, a man stormed police who were stationed outside the famous Champs-Elysees back in April. One French officer died in that incident, Fox News reported.

Just days ago, three attackers who said they supported the Islamic State allegedly plowed through pedestrians on the iconic London Bridge in London, killing seven people and injuring dozens more.

Multiple outlets reported Tuesday that French counter-terrorism police are now handling the Notre Dame attack investigation.

This is a developing story and will be updated.