"This is an existential threat and it's not new. There is a very organised campaign to sabotage the election," Nizami said during an interaction with members of the foreign media.
There is a "clear and present danger" from militants, who want to "eliminate candidates" and frighten voters, he said.
Over the past few days, the banned Tehrik-e-Taliban Pakistan and other militant groups have targeted campaign offices and election meeting in different parts of Pakistan.
Eight persons were killed in a suicide attack in Peshawar this morning while 12 people died and more than 40 were injured in four bomb attacks yesterday, heightening concerns about security for the May 11 general election.
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Nizami said the caretaker government was working closely with security and intelligence agencies to provide security to candidates and to foil the plans of militants.
He referred to Pakistani Taliban spokesman Ihsanullah Ihsan's warning that militants would target certain secular parties and said the administration had ensured that candidates were "adequately protected".
However, he acknowledged that some parties had complained that they were not being provided a level playing field because of the militant threats, and that campaigning was only being done in Punjab province.