The government did not specify which users or messages had prompted the ban on the microblogging site or why it was allowed to operate again so quickly.

Any representation of the Prophet Mohammad is deemed un-Islamic and blasphemous by many Muslims, who make up the overwhelming majority in Pakistan.

Pakistan blocked access to Facebook in May 2010 for nearly two weeks because of users conducting a competition on drawing Mohammad. Twitter, YouTube and about 1,000 other websites were also blocked for carrying blasphemous content.

The Internet Service Providers Association of Pakistan said its members had been asked to block Twitter indefinitely, but no reason was provided by the government.

Interior Minister Rehman Malik, an active Twitter user, said on the website Sunday night that he had intervened and asked the prime minister to order an end to the ban.

"Dear All yes I spoke to PM and informed how people are feeling about it.PM ordered to reopen the twitter," Malik tweeted. (twitter.com/#!/SenRehmanMalik/status/204265436056002560)

(Reporting by Qasim Nauman; Editing by Rebecca Conway and Nick Macfie)

• A Permanent Economic Emergency