Buildings moved for a few seconds during the short temblor. It was not immediately clear if it caused any damage.
The US Geological Survey in Golden, Colorado, said it hit at 1.23am (2023 GMT Wednesday) and measured its preliminary magnitude at 5.6 and said it was centred 135km north of Islamabad, 10km beneath the surface.
Saturday's 7.6-magnitude quake demolished whole towns, mostly in the Himalayan region of Kashmir.
The aftershock was also felt in Abbotabad, in the foothills of the area worst hit in the main quake, where it shook buildings but did not appear to cause any damage.
The death toll from Saturday's quake was believed to be
more than 35,000, and tens of thousands more were injured.
Saturday's quake was centered about 100km northeast of Islamabad in the forested mountains of Pakistani Kashmir. At least 22 aftershocks followed within 24 hours, including a 6.2-magnitude temblor.
In Islamabad, about a dozen men worked through the night for survivors from a 10-storey apartment building that collapsed.
They pulled out two bodies, which they quickly covered in burial shrouds, but found no signs of life. One of the victims was identified by searchers as a woman of dual Norwegian-Pakistani nationality.
A landslide buried and killed six Indian soldiers while they were searching for quake victims in India's portion of Kashmir on Wednesday.
Still, miracles continued amid the misery, with a Russian team rescuing a five-year-old girl in Muzaffarabad, the capital of Pakistan's portion of divided Kashmir, who had been trapped for nearly 100 hours in the rubble.
President Pervez Musharraf meanwhile appealed for more international aid for victims of Saturday's earthquake and called on his countrymen to unite to face one of the worst tragedies in its history.
President Musharraf appealed
for more international aid
Musharraf asked for more donations from Pakistanis and from overseas on Wednesday to a special fund set up to pay for rescue, relief and reconstruction, expected to cost hundreds of millions of dollars.
"I appeal to the nation to generously contribute to this fund. I would specially appeal to the business community, traders and industrialists," he said.
"I appeal to the international community to donate funds, give financial assistance ... to the president's relief fund."
Musharraf, who unlike past civilian leaders is untainted by allegations of corruption, promised that the fund would be handled with transparency.
Pakistan has received pledges of $350 million from abroad for Saturday's quake, and the fund has raised $16.6 million locally, Prime Minister Shaukat Aziz said earlier on Wednesday.
Musharraf thanked countries that had donated but singled out Indian Prime Minister Manmohan Singh for his offers of help, a significant gesture within the context of the peace process the two leaders are engaged in to end their countries' long enmity.
"We express our gratitude to him and we have accepted the Indian aid in certain form and have informed them," he said.
Speaking on the sixth anniversary of the coup that brought him to power, General Musharraf defended rescue efforts in the face of complaints over delays in relief operations and reminded Pakistanis of the remote location of the worst-hit areas.
"This tragedy is much bigger than the capacity and capability of the government as a whole. We have to face this challenge," he said in an address to the nation.
"I appeal to the international community to donate funds, give financial assistance ... to the president's relief fund"
"Those who died cannot come back, but it is in our hands to work for a better future of the affected areas and their people. And Insh Allah (God willing), we will succeed," Musharraf said.
The government reckons 2.5 million need new houses, and Pakistani officials said new cities will be built, but the task now was to provide tents for shelter, said Musharraf.