People in Paris took to social media to find and offer refuge on Friday night, as the city was gripped by chaos following a string of attacks that left dozens dead.

The Twitter hashtag #porteouverte, which means "open door" in English, was being used to offer shelter as authorities urged people to evacuate the streets. The hashtag trended globally, with more than 400,000 Tweets using it, in the few hours since its creation.

"This account will be used for tweeting and retweeting places to stay safe tonight," said a post from @PorteOuverteFRA, a Twitter handle opened within hours of the attacks.

Dozens of addresses and phone numbers for apartments were being tweeted on the handle, and it was retweeting offers of accommodation from other individuals.

A post from @LaraPlowright, written in mixed English and French, read: "Anyone stuck around gare du nord area, si besoin (if needed) #porteouverte quartier Gare du Nord, peut loger 2-3 personnes (can accommodate 2-3 people)."

Other posts on the tag said taxis were offering free transport for anyone in need a lift to shelter.

Still, some people found the process confusing amid the chaos.

"I'm not using the tag at the moment, but people are stuck in various areas and cannot leave, I hear," said Alessandra Gargiulio, who was waiting for her landlord's permission to open up her apartment for the night.

Gargiulio, 24, lives in the 24th arrondissement on the other side of the city from the attacks, but said she could see and hear helicopters and sirens from her apartment. She spoke to Reuters via Facebook messenger.

"We're super scared here, it's hell, but we'll use the tag and it's worth trying everything," said Maria Vittoria Zanetti, 23, who had just become aware of the tag. Zanetti, also contacted over Facebook, is stuck at a friend's apartment in the 2nd arrondissement.

Both Gargiulio and Zanetti, 23, have used the Facebook Safety Check to let friends know they are safe.