Pakistan Army fanned out across the country ahead of Wednesday’s election, deploying hundreds of thousands of troops to oversee polling stations in a short but acrimonious contest that analysts say is still "up for grabs".

Armed soldiers watched closely as election officials in the capital Islamabad Tuesday distributed ballot boxes and voting materials for polling stations across the city.

The armed forces have stationed over 370,000 personnel nationwide to ensure the vote goes smoothly — the largest such deployment in Pakistan’s history on an election day.

"Deployment of troops completed across the country," the military said in a statement late on Monday, saying the troops would work with local law enforcement to ensure "a safe and secure environment" for voting.

Despite controversies and bloodshed, political parties continued to criss-cross the country in the final days before the polls, holding dozens of rallies in key battleground areas.

The contest has largely been distilled to a two-party fight between jailed former prime minister Nawaz Sharif’s incumbent Pakistan Muslim League-Nawaz party, and cricketing legend Imran Khan’s Pakistan Tehreek-e-Insaf.

"Our predictions are very murky right now," Bilal Gilani, executive director of Gallup Pakistan, told AFP, adding that a huge chunk of voters remain undecided. "It’s still up for grabs."

Political parties held their final rallies Monday night — before campaigning was suspended — in a last-ditch attempt to energize voters.

"I am giving this task to all of you to wake up early on the 25th and cast your vote," Khan told thousands of party faithful in the eastern city of Lahore.

In southern Punjab, PML-N leader and brother of the former premier Shehbaz Sharif said victory was "certain".

"Despite all the odds PML-N is winning the July 25 polls," he was quoted as saying by Pakistani media.