[Update] Nice terror attack: What we know so far

French President François Hollande has ordered a three-month extension of the country's state of emergency following the terrorist attack that killed at least 80 people in Nice and left over 100 others injured on Bastille Day.

Hollande made the announcement after saying that the attack in the French Riviera city was “undeniably” of “terrorist nature.”

“France as a whole is under the threat of Islamic terrorism,” he said on national television. “We have to demonstrate absolute vigilance and show determination that is unfailing.”

To recall, a white truck drove into a festive crowd gathered along Promenade des Anglais at 22:30 Thursday just after the beachfront fireworks display ended as part of the celebration of French National Day.

Read more: BREAKING NEWS: Truck rams into crowd on Bastille Day, killing 77 in Nice

Local authorities initially reported 30 fatalities, but French Interior Minister Bernard Cazeneuve has put the death toll at 80 five hours after the incident. At least 18 victims are in “critical condition” as of press time.

Police shot dead the truck driver, who reportedly drove the truck two kilometers into the crowd. The identification of the perpetrator is still underway.

Earlier on Thursday, Hollande ordered the lifting of the state of emergency over France due to the beefed up security measures the country has adopted since the November 13 attack in Paris. At least 130 people died from the simultaneous attacks on the Bataclan music hall, Paris bars and restaurants, and the Stade de France football stadium, that were perpetrated by Islamist militants.

But due to recent developments, Hollande withdrew the order and called on military and police reservists to relive government forces that have been worn out due to the eight-month-long state of emergency.

“Nothing will lead us to give in to our will to fight against terrorism,” Hollande said, adding that France's efforts agains Islamic extremists.

On Twitter, Hollande said “France is is tearful, sorrowful, but it is strong and will be always more than the zealots who now want to hit her.”

World leaders, celebrities and ordinary citizens expressed grief over the tragedy. Acts of solidarity with France has been evident, even on social media. The #PrayForNice has been trending worldwide on Twitter alone.

French authorities have yet to disclose the identity of the fatalities. In the meantime, residents were advised to remain clam and to stay indoors while police operations progress.

WATCH: Truck drives into festive crowd in Nice on Bastille Day