Live Blog: Nice terror attack

At least 84 people were killed-- including two Americans-- and several others were seriously injured Thursday when a terrorist drove a large truck loaded with guns and hand grenades into a crowd that had gathered for a Bastille Day fireworks display in the southern French city of Nice.

Here's what we know so far:

• There is no immediate claim of responsibility, but two sources, including a U.S. counterterrorism source who collects and monitors jihadist social media, told Fox News that accounts linked to ISIS were "celebratory" and their followers were told to use the hashtag "Nice".
• The death toll of 84 was confirmed by French President Francois Hollande in a televised address Friday. Hollande added that 'there about 50 people who are very critically injured between life and death.'
• Nice's regional president Christian Estrosi said that more than 10 children were among the dead. A children’s hospital in Nice said it had treated some 50 children and adolescents injured in the attack.
• Two Americans were killed in the attacks, a US intelligence official tells Fox News.
• The driver was a 31-year-old Nice resident of Tunisian origin.
• Hollande also announced that he would extend France's state of emergency by another three months, until Oct. 26.
• France has been on its highest state of alert since ISIS terrorists killed 130 people in Paris this past Nov. 13.
• A U.S. official tells Fox News that the attack was in line with ISIS, which has become "increasingly brazen" in its attacks as it comes under increasing military pressure in Iraq and Syria.