Internet service providers in the U.S. experienced a service slowdown Monday after fiber-optic cables near Cleveland were apparently sabotaged by gunfire.

TeliaSonera AB, which lost the northern leg of its U.S. network to the cut, said that the outage began around 7 p.m. Pacific Time on Sunday night. When technicians pulled up the affected cable, it appeared to have been shot. "Somebody had been shooting with a gun or a shotgun into the cable," said Anders Olausson, a TeliaSonera spokesman.

The damage affected a large span of cable, more than two-thirds of a mile [1.1 km] long, near Cleveland, TeliaSonera said.

The company declined to name the service provider whose lines had been cut, but a source familiar with the situation said the lines are owned by Level 3 Communications Inc. Level 3 could not be reached immediately for comment.

Cogent Communications Inc. warned that some customers may be experiencing disruptions because network lines had been cut somewhere between Montville, Ohio, and Cleveland. "Splice crews are currently doing preparation work on the new fiber cable before splicing begins to resolve the outage," Cogent said in a note to customers.

According to Keynote Systems Inc.'s Internet Pulse Report , Cogent was experiencing significant latency problems on Monday.

The outage caused headaches for Christopher McCoy, a system administrator for a Web hosting company in Atlanta. "This Telia outage is really causing a pain," he wrote in a blog posting. "Telia is one of my company’s main network providers, and explaining to your average Webmaster the details and specifics of a fiber break isn’t all that easy."