London, United Kingdom - Dozens of British nationals, many of them dependent on complex medication to survive, are stranded indefinitely in Pakistan due to new border restrictions imposed by Islamabad to stem the coronavirus pandemic.

Pakistan, on Saturday, abruptly halted inbound international, chartered and private flights until at least April 4, a move which also disrupted most outbound flights.

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Meanwhile, several British nationals in Pakistan had booked tickets to travel on Emirates airline to return to England, but that carrier on suspended all flights on Sunday.

By Monday, as the UK announced a lockdown, the Foreign Office advised British nationals abroad to return to home - but for many, this advice came too late, as borders across the world had already been tightened to contain the spread of COVID-19.

Suhaiymah Manzoor-Khan, a writer, is among those stranded in Pakistan.

Within hours of creating an email account to communicate with other British nationals, at least 130 people contacted her, among them doctors eager to return to help combat the pandemic and Britons with serious health issues.

"The thing that is recurring is that a lot of these people have underlying health conditions. They're (the British High Commission) going to have a lot of blood on their hands because there's a lot of people here with health concerns and low medical supplies," Manzoor-Khan told Al Jazeera by phone, adding that she felt "abandoned" by the High Commission.

"I am worried. I'm here with my little brother and elderly grandma, she's 83. We can stay self-isolated and go to shops. But the government advice [in Pakistan] has only just become quite serious. Even so, I don't feel confident about accessing healthcare here."

On Tuesday, Al Jazeera found only a handful of outbound flights from Pakistan to the UK, available on Qatar Airways. But the cost of these single flights was upwards of 1,000 pounds ($1,174), an unaffordable price for many who have already paid out large sums for previous bookings.

Aisha Khan (not her real name), a 48-year-old from Birmingham, is asthmatic and dependent on insulin. She was set to return to the UK on April 8, but after the new restrictions were enforced in Pakistan, she wanted to arrange an earlier flight.

She travelled to Islamabad International Airport to make a new booking but was told by flight attendants to return to Azad Kashmir, where she had been staying, until further announcements.

With only a temporary supply of insulin and asthma pumps, enough to last two to three weeks, Jan said, "My asthma is unstable. If anything triggers me, I end up in intensive care. It's really worrying ... We just want to get back to our family."

Muhammad Asad (not his real name), is a kidney transplant patient stuck in a remote village near Islamabad. He was due to fly back to the UK on March 28 on Emirates.

"Because I'm a kidney transplant patient, I desperately need my immunosuppressant medication. I wasn't sure how much extra I had brought with me," he told Al Jazeera.

He tried "every avenue", including asking relatives from the UK to send his medication to Pakistan by post, and finally secured a month's supply from a specialist hospital in Islamabad.

As someone who has received an organ donation, and is, therefore, at high risk from the coronavirus, Asad is among the 1.5 million Britons who have now been advised by the UK government to self-quarantine for at least 12 weeks in total isolation - something he will do when he is finally able to return home.

But like many others, he feels frustrated by the lack of decisive action from the Foreign Office.

"If people with low immune systems board these flights, they're damned with the coronavirus around," Asad said. "The other dilemma is if I go on a plane with the virus circulating, I'm also under threat of picking it up."

Several people who contacted the British High Commission in Pakistan asking for help on Twitter have received the same copy and pasted message: "Please contact your travel company or transport provider as soon as possible for the latest information on available options. Speak to local travel companies in Pakistan. Contact your airline. Plan ahead, but be prepared that your plans may need to change."

In Pakistan, there are more than 900 confirmed cases of coronavirus and at least seven people have died from the COVID-19 disease.