Pakistan's mobile operators are scrambling to block text messages containing any of more than 1,600 "obscene" terms banned by the country's telecoms authority ahead of tomorrow's deadline.

The list, including words from "quickie" to "fairy" to "Jesus Christ", was distributed on November 14 with operators given seven days to comply, but has met with widespread derision and a threat of legal action.

"There are more than 1,600 words in the list including indecent language, expletives, swear words, slang etc, which have to be filtered," an official at a telecoms firm said on condition of anonymity because he was not authorised to speak to the media.

"The filtering is not good for the system and may degrade the quality of network services - plus it would be a great inconvenience to our subscribers if their SMS was not delivered due to the wrong choice of words."

Other words and phrases on the list of 1,695 terms, issued in English and Urdu, include "athlete's foot", "idiot" and "damn", as well as "deeper", "four twenty", "go to hell", "harder" and "looser".

PTA officials were unavailable to comment on the ban, which did not appear to have been implemented on Sunday as messages containing the words were still transmitted.

The letter accompanying the list says networks must also submit monthly reports on implementation.

Campaign group Bytes for All said it would challenge the order in court, saying it violated rights to free speech and privacy.

"We are now witnessing a new ruthless wave of moral policing in the digital communication sphere of Pakistan imposed by the Pakistan Telecommunication Authority," country coordinator Shahzad Ahmed said.

"By developing extremely detailed lists of allegedly 'offensive' words and forcing telecom operators to filter them out to make our society moral and clean, PTA has not only made a mockery of itself but also of the entire country and its government."

The move in the Muslim-majority country sparked derision from local Twitter users.

"Maybe all Pakistanis should keep sending expletive-filled text msgs every 10 minutes and wait for the networks to collapse," tweeted user Shoaib Taimur.

"Seriously, why aren't we protesting this ban? Jokes apart, they've banned words that have no vulgar implications whatsoever," tweeted Sara Muzzamil.

Several Twitter users also questioned the inclusion of the term "ass puppy" on the list, saying they had never heard of it.

It is the first time the country has sought to censor text messages but the PTA has previously blocked websites deemed pornographic or offensive to Islam.

Pakistan blocked Facebook for nearly two weeks in May last year in a storm of controversy about a competition to draw the Prophet Mohammed and has restricted access to hundreds of websites because of blasphemy.

The country briefly banned YouTube in February 2008 during a similar outcry against cartoons of the Prophet Mohammed.

AFP