The offending tweets, according to Pakistani officials, involved a contest to draw cartoons of the prophet Muhammad. Many Muslims consider any depiction of the prophet to be blasphemy.
Pakistan's newly appointed Minister for Information Technology, Raja Pervez Ashraf, issued a blanket ban on the site inside the country, upping the pressure on Twitter as negotiations continue.
Censorship is nothing new in Pakistan, but often it surrounds matters tied to the country's powerful security establishment. In this case, activists suspect the democratically elected civilian government is using the sensitive topic of blasphemy as cover for constricting the space for political debate ahead of national elections.
"The government is trying to test the waters to see what the response on such censorship is. We foresee more control on access of information, like we have seen in the past, when elections are near," says Shahzad Ahmad, head of Bytes for All, an organization that monitors Internet freedom in Pakistan.
Twitter has emerged as a key forum where subjects once thought to be taboo could be openly discussed without fear, says social media campaigner Nukhbat Malik. According to her, the mainstream media in Pakistan has avoided discussing issues like sectarian violence, criticism of the military establishment, and sensitive social issues like rape and child abuse.
Authorities have pounced on the blasphemous cartoons as "a lame excuse" to rein in the much broader, free-wheeling discourse on Twitter, says Ms. Malik, who works for Internews, an American organization focusing on empowering local media in Pakistan.
"Pakistan has always been a security state whether there is democracy or not," she adds.
The chairman of the Pakistan Telecom Authority (PTA), Muhammad Yaseen, says the IT minister is in negotiations with Twitter officials. "We are trying to resolve the situation, but I cannot give a time frame of when the ban will end."
Until then, the country's Internet service providers have been directed to block the site. That order drew criticism from Wahaj-us-Siraj, spokesperson for the ISPs Association of Pakistan, who argues the government could have chosen more limited blocks.
"[The] public in Pakistan is very sentimental about religion, but [the government] could have asked us to block particular pages, if there was any such content. But we have to follow law of the land," says Mr. Siraj, adding that blasphemy is a punishable offense in the country.
This is not the first time the country has restricted Internet freedom, with Facebook being blocked for similar reasons in 2010. Content criticizing the Pakistani military on YouTube and on Rolling Stone magazine's website have also drawn bans, as have websites calling for independence for Balochistan Province.
According to independent sources around 13,000 websites are current inaccessible in the country. The PTA puts the figure much lower, stating that around 2,000 sites are banned in Pakistan.
Mr. Ahmad, the Internet freedom activist, has set up a team of IT professionals who are helping people bypass the Twitter ban.
"We want people to continue using Twitter in protest of blocking it. Also, journalists, human rights activists, and other such professionals need Twitter for their work, and we want to help them maintain the access," he adds.
While activists are calling an end to the ban, elected officials in the parliament say they were not even taken into confidence over this.
"The ban on Twitter is outrageous," says Bushra Gohar, who is a member of the National Assembly of Pakistan and belongs to a coalition partner of the federal government of Pakistan.
"This is in violation of human rights, and the state is acting as if the public are delinquent children who need to be controlled," Ms. Gohar adds.
She tried reaching government officials to register her protest, but to no avail. "Pakistan has a democracy, not a dictatorship. But it feels like the latter," Gohar says.