When British colonial rule ended in 1947, India was divided to create a separate homeland for Muslims in the form of West Pakistan and East Pakistan - now Bangladesh.
An estimated 10 million people crossed the borders in both directions - one of the largest such migrations in history, and one accompanied by violence that killed 500,000 to one million people.
Security is tight in public places, fireworks were banned and public gatherings were being kept to a minimum, police in the capital and other cities said.
"This year the threats are serious," said Aftab Cheema, police chief in the eastern city of Lahore.
"We have therefore deployed police in plain clothes and installed closed-circuit cameras at key places to avert an incident in major cities and towns."
One of the largest ceremonies was expected to take place at Wagah, near Lahore and the overland crossing with India, where crowds from both sides were to greet each other at a flag-raising ceremony.
Shaukat Aziz, the Pakistani prime minister, who opened the ceremony, told a gathering of hundreds of government officials, school children and others that Pakistan took pride in being the only Muslim country to have nuclear weapons.
"All these man-made boundaries were drawn for some selfish motives"
Ussudoor, Riyadh, India
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"Our nuclear assets are symbols of our national honour and sovereignty," Aziz said.
"The nation has always displayed solidarity and unity for them. And we will never tolerate that anyone should look with a dirty eye at our nuclear assets."
"We will never allow any foreign power to interfere in our frontiers," Aziz said, highlighting the issue of possible unilateral US strikes against targets in Pakistan.
He also said Pakistan would show respect to its neighbours, an apparent reference to India.
On the eve of independence day, Pakistan sent home 134 Indian prisoners who had crossed the border illegally, as part of ceremonies marking the two countries' 60th anniversary.
India was also expected to return Pakistani prisoners on Tuesday.
In recent years, Pakistan and India have engaged in a series of negotiations aimed at normalising relations and settling a bitter dispute over the Himalayan region of Kashmir.
Independence celebrations take place as Pakistan heads toward presidential and legislative elections.
Pervez Musharraf, Pakistan's president, and close ally of the US in its "war on terrorism", is seeking another term as the military head of state, but faces one of the toughest periods in office since taking power in a bloodless coup in 1999.
Musharraf's bid earlier this year to remove the Chief Justice Iftikhar Mohammed Chaudhry backfired, drawing street protests, as the Pakistani supreme court reversed Musharraf's move.
The Pakistani president also faces pressure from Washington to do more to tackle al-Qaida and Taliban fighters in Pakistan's northwest tribal region bordering Afghanistan.
Then, there is the wave of violence that has killed more than 380 people since early July.
In a statement marking the anniversary of creation, Musharraf urged Pakistanis to reject extremism at the coming elections.
He said: "I urge all Pakistani citizens to get involved in the electoral process and become the instruments of enlightened moderation in their beloved country."