There were no immediate reports of injuries or damage from the tremors.
The heaviest aftershock, with a magnitude of 5.2, came at 6:43 am (0143 GMT) and there were three weaker tremors between 5:00 am and 9:00 am, Qamaruz Zaman, chief of the country's seismological department, told AFP.
Witnesses said the biggest shock woke people from their sleep in the capital Islamabad and the devastated city of Muzaffarabad.
"An aftershock with a magnitude of more than five can cause landslides in the hilly terrain," Zaman said. "The fear is that landslides will further hamper our operations," World Food Programme spokesman David Orr told AFP in Muzaffarabad.