The Bahrain Telecommunications Co said its services were affected after two undersea cables were cut near Alexandria, on Egypt's north coast.
"This cut has affected internet services in Egypt with a partial disruption of 70 per cent of the network nationwide," the Egyptian ministry said in a statement.
The Egyptian telecoms ministry said it did not know how the cables were cut or if weather was a factor.
Storms had forced Egypt to close the northern mouth of the Suez Canal on Tuesday.
India reported serious disruptions to its services, with Rajesh Chharia, the head of an internet-service providers' body, saying: "There has been a 50 to 60 per cent cut in bandwidth."
He said a "degraded" service would be up and running by Wednesday night, but full restoration would take 10 to 15 days.
"The big operators have transferred their small broadband connectivity through the Pacific route, and that's the reason there's no hue and cry in the country," he said.
AT&T said that a cable owned by a consortium of which it is part was affected.
"We do know that one cable is disrupted," Michael Coe, an AT&T spokesman, said.
He said the "cable in question goes between France and Egypt".
Egypt said its call centres saw their services cut by more than 30 per cent, and two Egyptian stock brokers said market transactions were considerably slower and some international trading orders could not go through.
In Cairo, much of the capital city was without access to the internet for the bulk of the day, frustrating businesses and the professionals.