Pakistani cable television operators have begun blocking the BBC's international news TV channel, BBC World News.
The operators say that the move is in response to a documentary broadcast by the channel, entitled Secret Pakistan.
Other foreign channels broadcasting "anti-Pakistan" material have been warned that they too will be blocked.
The BBC said it was deeply concerned by the move, and called for its channel to be speedily reinstated.
"We condemn any action that threatens our editorial independence and prevents audiences from accessing our impartial international news service," a BBC spokesperson said.
"We would urge that BBC World News... to be reinstated as soon as possible."
The two-part BBC documentary questioned the country's commitment to tackling Taliban militancy.
It argued that some in Pakistan were playing a double game, and quoted US intelligence officials as saying that they had acted as America's ally in public while secretly training and arming the Taliban in Afghanistan.
Correspondents say the Pakistani government is likely to have put pressure on the operators to impose the ban, although Pakistan has denied this.
The country's High Commission in London said the cable operators had taken the decision to block BBC World News on their own.
"The government of Pakistan strictly believes in the freedom of press and media," said a statement from the High Commission.
The decision to block BBC World News and the warning to other international news channels come after a media uproar in Pakistan over a Nato air strike that killed 24 Pakistani troops near the Afghan border at the weekend.
The All Pakistan Cable Operators Association announced on Tuesday that all foreign news channels airing "anti-Pakistan" content would be barred from Wednesday.
The operators called on the Pakistan Electronic Media Regulatory Authority (Pemra) "to revoke the landing rights of foreign channels" if they were found to be "propagating" information harmful to the country.
Relations between Pakistan and the US in particular, and the West in general, have been strained by the raid - as well as by continuing US drone strikes in Pakistan, the killing of Osama Bin Laden in May and a row over a CIA contractor acquitted earlier this year after killing two men in Lahore.
Correspondents say it is not possible to see BBC World News in most Pakistani cities, with the ban expected to be extended to rural areas by Wednesday.
Cable Operators Association spokesman Khalid Arain said that no anti-Pakistan foreign channel would "ever" be broadcast in the country.
He said BBC World News would only be put back on air if the corporation offered assurances that it would not broadcast anything "against Pakistan".
BBC World News is thought to be the only foreign channel taken off air so far.