LAHORE - Pakistan suspended mobile phone and data services nationwide on Thursday for election day, in a move a digital rights group said was "inherently undemocratic".
A statement from the interior ministry said "precious lives have been lost" in recent militant attacks and such "security measures are essential to maintain the law and order situation and to deal with potential threats".
Nighat Dad, a lawyer who runs the not-for-profit organisation Digital Rights Foundation, said the outage "is an attack on the democratic rights of Pakistanis".
"Shutting down mobile phone services is not a solution to national security concerns. If you shut down access to information you create more chaos. How do you call (anyone) if, God forbid, there is an attack?"
She added that there is more room for disinformation to spread, including about reports of unconfirmed attacks.
"People will of course put their safety first if they are unable to verify rumours of an attack in their area," she said, noting such disinformation could cause voters to stay away from the polls.
Bilawal Bhutto-Zardari, head of the family-run Pakistan Peoples Party (PPP), demanded the government restore services and said party lawyers would challenge the decision in court.
Voters in Pakistan rely on a text messaging service to confirm the polling station where they are registered to vote.
NetBlocks, a global internet watchdog, said data confirmed there was a disruption to mobile phone and internet services "corroborating widespread user reports of outages".
"The ongoing election day internet blackout in Pakistan is amongst the largest we've observed in any country in terms of severity and extent," NetBlocks director Alp Toker told AFP.
"The practice is inherently undemocratic and is known to limit the work of independent election observers and cause irregularities in the voting process."