Land and mobile telephone lines are down in Islamabad, reports say.
Private channels Geo News and Dawn News earlier quoted unnamed sources as saying the government had made up its mind to declare emergency rule. Shortly afterwards they came off air.
Parliamentary elections are due in January - it is not clear whether they will go ahead.
http://news.bbc.co.uk/2/hi/south_asia/7076670.stmDozens of police blocked the road in front of the court building, with the judges believed to be inside. Unconfirmed reports from Geo indicated the army had entered the court building.
The government blocked transmissions of private news channels in the capital and other cities.
Shahzad Iqbal, an official at a cable TV news provider in Islamabad, said the authorities were blocking transmissions of private news channels in Islamabad and neighbouring Rawalpindi. State TV was still on the air.
"The government has done it," he said. Residents of Karachi said their cable TV was also off the air.
http://www.guardian.co.uk/international/story/0,,2204802,00.html