The Philadelphia-based company said Monday that congestion resulting from the calls has forced it to reroute phone traffic as it tries to identify the carrier whose telephone numbers are generating them.
Comcast Corp. spokeswoman Kristen Roberts says other local phone carriers in New Hampshire and Massachusetts also may be suffering as a result.
The outages come as political campaigns hit the phones to woo voters before Tuesday's midterm elections.
The New Hampshire Democratic Party says it lost phone service at local campaign offices at 11 locations around the state. A 2002 scheme to disrupt Democrats' get-out-the-vote efforts by jamming telephones with hang-up calls resulted in criminal convictions for a former state GOP executive director and a former political consultant.