A BBC correspondent said Sharif, who was ousted in a bloodless military coup by Pakistani President Pervez Musharraf in 1999 and sent into exile, was arrested after his plane landed in Islamabad and he was taken to a prison by helicopter.
After the plane landed, there was a nearly two-hour standoff with Sharif refusing to surrender his passport to immigration officials, the report said.
After two hours of questioning, a special flight was arranged to return Sharif to Saudi Arabia, Geo TV reported.
Sharif, who had planned to challenge Musharraf in the coming elections, was accused of money laundering and corruption.
CNN reported clashes with Sharif supporters near the airport led to the arrests of 635 people.
Prior to Sharif’s departure from London, Britain's Telegraph reported Pakistani authorities had rounded up some 2,000 of his supporters.
The extraordinary measures taken ahead of Sharif’s return reportedly included the cancellation of all domestic flights at Islamabad airport.