Computers have been turned back on in Atlanta, Georgia, but the city is still struggling with its ability to collect online payments of bills and fees, seven days after a ransomware attack snarled its computer system.

Hackers caused outages of services offered through the city's website and broader computer system while demanding a ransom of $51,000 paid in bitcoin to unlock the system.

"This is much bigger than a ransomware attack, this really is an attack on our government," Mayor Keisha Lance Bottoms told a news conference. "We are dealing with a (cyber) hostage situation."

She did not say whether Atlanta would pay the ransom. Atlanta officials said they have determined the hackers' identity but declined to elaborate. City representatives were not immediately available for further comment.

Bottoms said only that the hackers entered the city's digital system remotely as opposed to having had internal access.

Ransomware is a type of malware that infects computers or computer networks and then freezes them, with the attackers demanding a ransom in order to restore services. The initial assault often comes via a phishing link that someone within the network opens on their email.

As the disruption in Atlanta persists, the city is losing out financially, Bottoms told an earlier news conference last Friday. It was unclear how much it stands to lose or when the city expects to get its computer system fully operational again.