French people took to social media to find friends and relatives, search for shelter and tell the world they were safe on Saturday, after a wave of attacks across Paris left 128 people dead.
Internet users posted poignant appeals on Twitter to find their loved ones who had been at the scenes of the bloodshed, including at the Stade de France stadium and a rock gig at the Bataclan theatre.
"If anyone has news of Lola, aged 17, at #Bataclan this evening, contact us," read one post, while another expressed concern for a friend Thibault, who was also at the concert. "He's not getting back to me: help me," it read.
Other Twitter feeds remained ominously silent after announcing the start of the concert at the Bataclan concert hall, where at least 82 people were later killed by gunmen wielding AK47s.
Eight attackers struck numerous locations around the capital, leaving at least 120 people dead on Friday night, the bloodiest such incident in Europe for more than a decade.
Thousands of Parisians used the hashtag #PorteOuverte (open door) to organise places to stay for people who had been left stranded -- particularly in areas that had been attacked.
The hashtag was re-posted 480,000 times as the hours passed with the city on lock down, making it the second-most used keyword on Twitter in France after #fusillade (shooting) which was used 700,000 times.
"If people are stranded, I can accommodate two or three people on Rue des Martyrs," offered one user, while Wrote GabDeLioncourt said: "Our sofa is always available for two/three people in Maraichers."
Others set up an emergency website "porteouverte.eu" to help people find temporary shelter.
Meanwhile, Facebook launched a "Paris Terror Attacks" check-in feature to let people signal whether they were out of harm's way, then notify their connections on the social networking site.
"Quickly find and connect with friends in the area," a message from the Facebook Safety Check service read. "Mark them safe if you know they're OK."
The feature also allowed people to check which friends listed as being in Paris had not yet checked in as safe.
"We are shocked and saddened by the events unfolding in Paris," a Facebook spokesman told AFP.
"Communication is critical in these moments both for people there and for their friends and families anxious for news."
The ISIS militant group, centred in Iraq and Syria, claimed responsibility for the attacks, the deadliest Paris has seen since World War II.
Lebanon Terrorist attacks
Social media also played a role when suicide attacks struck a Shia neighbour on Thursday in Beirut, Lebanon, where at least 43 people died and close to 200 were injured.
Following the attacks, Twitter users in Lebanon used hashtags including "#We_decided_to_live as a show of unity against terrorist attacks, as well as for making requests for blood donations to aid the injured victims of the attacks.
Social media was also used in spreading images of the attacks, the largest Lebanon has seen since the mid 1990s.
The ISIS group has also claimed responsibility for these attacks, which it said targeted Shia citizens and supporters of the Shia militant group Hezbollah.