The Islamic State claimed responsibility for a terror attack Thursday night on Paris' famed Champs-Elysees, where one police officer was killed and two others were wounded by an assailant killed in the exchange of gunfire.

The assault in the popular tourist area came just  three days before a critical presidential election in which security has loomed as a major issue.

The Islamic State identified the attacker as Abu Yusuf al-Beljiki through its Amaq news agency, according to SITE Intel Group, a U.S.-based organization that monitors terrorists' activity online.

Paris police spokeswoman Johanna Primevert told the Associated Press that the gunman deliberately targeted police on guard near the Franklin Roosevelt subway station, and appeared to act alone.

Interior Ministry spokesman Pierre-Henry Brandet told BFM television that a man stepped from a car and opened fire on a police vehicle. A witness told Reuters that the attacker opened fire with a machine gun.

Security has been high in France since Tuesday, when police apprehended two men suspected of plotting an imminent terror attack. A French station hosting a televised event with the 11 presidential candidates briefly interrupted its broadcast to report Thursday's shooting.

The first round of a hotly contested presidential election takes place Sunday, with an independent and candidates on the far-right and far-left threatening to upend mainstream parties that have ruled France for decades. A string of terror attacks over the past 18 months has become a major issue in the campaign, along with concerns about France's high unemployment and rising immigration.

President Francois Hollande is not running for another term because his approval rating is so low.

As the terror attack unfolded, police blocked off key roadways in the heart of the French capital and told people to avoid the area. The broad avenues leading to the Arc de Triomphe were filled with police vehicles flashing blue lights.

French prosecutors opened a terrorism investigation into the attack. Two police officers told AP the attacker had been flagged as an extremist, but offered no further details. The officers spoke to AP on the condition of anonymity to share information about the ongoing investigation.

In Washington, President Trump said the shooting in Paris “looks like another terrorist attack."

"It just never ends, We have to to be strong and we have to be vigilant, and I've been saying it for a long time," Trump said.

France has lived under a state of emergency that was declared following multiple terrorist attacks in November 2015 that left 130 dead.