"The source of (the) signal blockage has been pinpointed to a Libyan intelligence agency building ... south of the capital Tripoli," said Al Jazeera, whose coverage of a regional political unrest has been watched across the Arab world.
"The media should be able to operate freely, so all interference with our work and our broadcast signal should cease forthwith," an Al Jazeera spokesman said.
There was no immediate response from Libya, as Libyan leader Muammar Gaddafi's four-decade-old rule appeared in increasing jeopardy as anti-government protests reached the capital for the first time and security forces killed dozens of people.
Jamming was being caused by large installations capable of simultaneously interfering with several frequencies on the Arabsat and Nilesat satellites, Al Jazeera said earlier.
The station has exhaustively covered events in Tunisia, Egypt, Libya, Bahrain and Yemen, contacting protesters and government backers by telephone and often airing footage sent over the internet.
Earlier this month, Egypt cut al Jazeera's Nilesat satellite signal for more than a week before a popular upheaval toppled Hosni Mubarak from power.
Launched in 1996, Al Jazeera has more than 400 reporters in over 60 countries, according to its website. It says it can reach 220 million households in more than 100 countries.
