A powerful 5.6-magnitude earthquake jolted several cities and northern parts of the country on Tuesday afternoon, leaving at least 23 people dead and over 300 others injured, officials said. At least 100 of those injured are in a critical state.

The tremors lasted for 8-10 seconds and were felt strongly, DawnNewsTV reported.

Prime Minister Imran Khan, who is currently in the US to attend the United Nations General Assembly, has expressed his grief over the loss of human life. Both he and Army Chief Gen Qamar Javed Bajwa have issued directives to civilian and military agencies for emergency rescue and relief efforts.

The epicentre of the shallow quake, which hit just after 4pm, was near the Azad Kashmir city of Mirpur, roughly 20 kilometres north of Jhelum in Punjab, according to data released by the US Geological Survey.

“The quake was 10 kilometres deep and was felt in most of Punjab province and some parts of Khyber Pakhtunkhwa. The worst hit was Mirpur, Azad Kashmir,” chief meteorologist Muhammad Riaz told AFP.

Other cities where tremors were felt included Islamabad, Mirpur, Peshawar, Rawalpindi, Lahore, Sialkot, Sargodha, Mansehra, Gujrat, Chitral, Malakand, Multan, Shangla, Bajaur, Swat, Sahiwal and Rahim Yar Khan.

Mirpur Deputy Inspector General of Police Sardar Gulfraz Khan said at least 23 people, three of them young children, were reported to have died and more than 300 others wounded due to the quake. The casualties were shifted to Divisional Headquarters Hospital Mirpur. At least 10 people died in Jatlan village alone.

Mirpur Divisional Commissioner Chaudhry Muhammad Tayyab said among the people being treated for their wounds, at least 35 have sustained critical injuries. The chief of the National Disaster Management Authority later put the number of critical injuries at around 100.

According to the NDMA chief, the nearby Mangla Dam, one of the country's two main water reservoirs, was unaffected by the quake.

Earlier, AJK Minister for Sports, Youth and Culture Chaudhry Mohammad Saeed had told Dawn that a state of emergency had been declared in state-run and private hospitals in Mirpur.

Saeed, who had returned from Mirpur city, said most of the injured were from the outskirts of Mirpur, such as Afzalpur, Jatlan and New City.

"People were panicked in the beginning, but they have gradually started adjusting themselves with the situation," he added.

He revealed that pharmacies in Mirpur are offering free medicines to the victims, in a gesture of humanity.

AJK Prime Minister Raja Farooq Haider, who was in Lahore since Monday to attend Kashmir-related events, cut short his visit and rushed to Mirpur “to supervise rescue, relief and rehabilitation services”, his office said in a statement.

“The prime minister has directed all government departments to leave no stone unturned in helping out victims of this [...] natural disaster,” the statement added.

'Devastating earthquake'

Photos and video carried by TV channels showed dozens of collapsed buildings and homes, uprooted trees and cracks in roads large enough to swallow cars in Mirpur.

Muhammad Safdar, 60, who lives near Mirpur, said he was in his house when it suddenly started shaking.“We saw walls and the roof developing cracks and ceiling fans and other articles falling down, and we rushed out into an open field,” he told Reuters by telephone. “I have never seen such a devastating earthquake in this area in my life.”

Ramzan Ahmad, 65, who suffered a head injury and bleeding nose, said that he was with his family of seven when his house collapsed.

“We all got injuries,” he said. “I saw dozens of houses razed on my way to hospital.”

Mirpur, a city known for its palatial houses, has strong ties to Britain with the majority of its 450,000 residents carrying both British and Pakistani passports.

A spokeswoman at the British High Commission told AFP they were monitoring the reports, while the US embassy offered its sympathies to those affected via Twitter.

Tremors felt in India

Tremors were felt as far as New Delhi, while the Press Trust of India reported that panicked people rushed out of their homes and offices in panic in several places, including in Rajasthan, Punjab and Haryana. According to DNA India, the quake was also felt in parts of Indian-occupied Kashmir and Uttar Pradesh.

“The earthquake was felt but there are no reports of any damage,” Amir Ali, from the disaster management department in occupied Kashmir, told AFP.

With occupied Kashmir's mobile and internet services mostly cut off after the region's autonomy was stripped by New Delhi in early August, people used social media to express fears about not being able to get in touch with their families in the valley.

“Dear @AmitShah (Home Affairs Minister) please restore mobile services in Kashmir I do not know any update since Aug 5 about my family. We are now feeling so anxious about our family in aftermath of Earthquake,” Faizan Peer tweeted.

Rescue efforts

The military's media wing had tweeted soon after the quake that Army Chief Gen Qamar Javed Bajwa has issued directions for troops to conduct an "immediate rescue operation" in aid of the civil administration for victims.

Army troops with aviation and medical support teams have been dispatched to the area, the statement had said.

In a later update, Inter-Services Public Relations said Pakistan Army aviation helicopters had completed aerial reconnaissance for damage assessment in Mirpur, Jarikas and Jatlan areas. Army troops have also reached these areas. "Relief and rescue efforts [are] underway," it added.

Prime Minister Imran, in a statement from New York, "expressed his profound sorrow over the damage and loss of precious lives" caused by the earthquake.

The premier also instructed the relevant departments to provide all possible assistance for relief in the disaster-struck areas.

The National Disaster Management Authority has also been instructed to speed up its relief operations in all areas hit by the earthquake.

Mangla Dam 'safe'

A Wapda spokesperson said Mangla Dam and its powerhouse have not suffered any damage in the quake.

"A team of experts has reached the site to conduct a detailed damage assessment and will prepare a report. They have, in the meanwhile, declared the site as safe and have reported no damage," DawnNewsTV quoted him as saying.

According to the spokesperson, the earthquake caused the turbine water to become polluted which is why it was turned off.

Power generation will resume as soon as the water and turbines are cleaned, he said.

Pakistan's vulnerability

Pakistan straddles part of the boundary where the Indian and Eurasian tectonic plates meet, making the country particularly susceptible to earthquakes.

In October 2015, a 7.5-magnitude quake in Pakistan and Afghanistan had killed almost 400 people, flattening buildings in rugged terrain, which impeded relief efforts.

The country was also hit by a 7.6-magnitude quake on October 8, 2005, which killed more than 73,000 people and left about 3.5 million homeless, mainly in AJK.

Social media updates

People in the capital and other cities took to social media to share how they experienced the earthquake.

With additional reporting by Sanaullah Khan in Islamabad and Adnan Sheikh in Lahore.