Shahbaz Taseer, who was under police protection, was taken from a wealthy neighbourhood of Lahore, the capital of the eastern province of Punja, while on his way to work.
His vehicle was intercepted by four men in a car in the city’s upmarket Gulberg area," said police emergency official Syed Mumtaz. "They overpowered him at gunpoint and forcibly put him in their car and sped away."
Police are said to be searching for the car but there was no indication of who may have been behind the daylight abduction.
Provincial law minister Rana Sanaullah said the Punjab government had provided Taseer with a police escort after his father was killed "but he did not ask them to accompany today".
He added it was too early to say who the abductors were.
Salman Taseer was killed by a bodyguard outside an Islamabad coffee shop for criticising the blasphemy law, which provides for the death penalty. It was the highest-profile political killing in Pakistan in more than three years.
Police officials said Taseer's family had been repeatedly threatened to withdraw the murder case against the police bodyguard accused of his killing.
US-based Human Rights Watch has confirmed the abduction. Its Pakistan director Ali Dayan said the federal and provincial governments "must ensure that the younger Taseer is recovered speedily and his abductors are held accountable".
Taseer's murder was followed two months later by the assassination of another vocal opponent of the law, minorities minister Shahbaz Bhatti, the only Christian in Prime Minister Yousuf Raza Gilani's cabinet.
The government backtracked on amending the blasphemy law in December after a number of popular protests despite criticism from rights groups who say it is often abused to settle personal scores.