President Obama on Friday pledged the United States would stand with France, its oldest European ally, and “destroy the vile terrorist organization” responsible for Thursday’s truck attack that killed 84 people, including two Americans.

Obama called the attack in southern France “appalling” and said it was “a threat to all of us.”

Obama said he had spoken with French President Francois Hollande earlier and told him the U.S. pledged its support to help defeat extremist ideologies and that America would “stand with our French friends.”

Obama also warned against calls made by some to expel Muslims  who believe in Sharia law from the U.S. and added that the suggestion is an “affront to everything we stand for as Americans.”

Former House Speaker Newt Gingrich responded to Thursday's deadly attack by saying the U.S. should deport Muslims who believe in Sharia. He said Sharia is "incompatible with Western civilization."

Obama made the comments during a White House reception Friday for diplomats from around the world. He added that the world “cannot give into fear or divide ourselves, we cannot do their jobs for them.”

French officials say Thursday’s massacre was an undeniable act of terror, but no group has claimed responsibility and it wasn’t clear if the 31-year-old delivery driver blamed for the carnage had extremist ties.

The country is still reeling from the Nov. 13 attacks that killed 130 people at the Bataclan concert hall, Paris restaurants and cafes, and the national stadium, and a separate January 2015 iParis attack that targeted journalists at the satirical magazine Charlie Hebdo and Jews at a kosher supermarket.

Both attacks were claimed by the Islamic State group.

Hollande was booed in Nice on Friday by people who blamed government authorities for failing to enforce sufficient security measures.

The Associated Press contributed to this report.