Several US airport websites were temporarily down on Monday morning following a cyberattack reportedly carried out by Russian-backed hacking group Killnet. Officials said flights were not affected. The Atlanta and Los Angeles international airports were among airport websites impacted by the apparent coordinated denial-of-service attack.

Several other airports reported problems connecting to their websites or websites that appeared to be functioning very slowly, including Chicago’s O’Hare International Airport website, which was included on a target list published on Killnet’s Telegram channel.

“We noticed this morning that the external website was down, and our IT and security people are in the process of investigating,” said Andrew Gobeil, a spokesman for Atlanta’s Hartsfield-Jackson International Airport. “There has been no impact on operations.”

Portions of the public-facing side of the Los Angeles International Airport website were also disrupted, spokeswoman Victoria Spilabotte said. “No internal airport systems were compromised and there were no operational disruptions.”

Spilabotte said the airport notified the FBI and the Transportation Security Administration, and the airport’s information-technology team was working to restore all services and investigate the cause.

The Chicago Department of Aviation said in a statement that websites for O’Hare and Midway Airport went offline early Monday but that no airport operations were affected.

Last week, a group of hackers claimed responsibility for cyberattacks against state government websites across the United States.