The disruption was caused due to a fault in the main submarine cable near Jeddah, an official of Pakistan Telecommunication Authority (PTA) said.
Apart from hitting other activities, the interruption forced authorities to cancel two domestic and six international flights at capital's only airport.
An aviation official said flight schedule and bookings could not be confirmed due to slow internet, which resulted in cancellation of flights.
The air traffic would become normal after full restoration of internet services.