At least one person was killed in a Saturday morning blast outside the Italian consulate in Cairo; four others were injured.

According to an Italian diplomat, the country's consulate in the Egyptian capital was closed at the time and no staff members were wounded or killed in the 6 a.m. blast.

The exact cause of the explosion was still unclear, a security official said. A separate anonymous security official told the state-owned Middle East News Agency that investigators are looking into the possibility of a car bomb.

Online supporters of an Islamic State affiliate in Egypt have claimed responsibility for the blast, saying it was a car bomb. The authenticity of the claim could not be immediately verified, but mirrors similar claims made by the group about prior attacks. Italian Foreign Minister Paolo Gentiloni vowed his country would not be intimidated after the explosion.

"Our thoughts are with the people affected and with our personnel. Italy will not let itself be intimidated," Gentiloni wrote in a message on his official Twitter feed.

According to the Associated Press, the Italian consulate — which became so after World War II — sits on one of the busiest intersections in downtown Cairo.

The U.S. Embassy in Cairo has condemned the car bombing at the Italian consulate in Cairo that killed one person, telling AP: "We extend our condolences to the family of the victim of this attack and wish the injured a speedy recovery. We reiterate our steadfast support for Egypt in its fight against terrorism."