Around 170,000 people signed up within hours of a British government call for volunteers to help those stuck at home due to the coronavirus outbreak, the health minister said Wednesday.

Matt Hancock unveiled a plan on Monday to create a 250,000-strong volunteer force to help deliver groceries and medicines to the most vulnerable people instructed by the government to self-isolate.

This is larger than Britain's armed forces, which currently stand at just over 192,000.

"We're delighted that overnight 170,000 people have signed up to volunteer to support our NHS tackling coronavirus," Hancock tweeted, referring to the state-run National Health Service (NHS).

The government has closed all non-essential shops and services and told people to stay at home to try to stop the spread of COVID-19, after 422 deaths and more than 8,000 cases in Britain.

Special advice has been drawn up for 1.5 million people considered most at risk because of underlying health conditions, asking them to entirely avoid social contact.

Under the new NHS Volunteers scheme, healthcare professionals and some charities will be able to request help for their at-risk patients, who will then be matched with volunteers who live near them.

Any adults who are fit and healthy can apply to help deliver medicines from pharmacies, drive patients to appointments or make regular phone calls to check on people.

"This is one of those once-in-a-lifetime moments where a single action from one person can be the difference between life and death for another," said Nikki Kanani, head of NHS primary care services.

"Simple acts of kindness are going to make all the difference in keeping some of the most vulnerable people well and out of hospital.

"NHS staff are pulling out all the stops to ensure those who need care receive it, and creating a bank of helpers that they can call upon to support their most vulnerable patients through this difficult time is going to be invaluable."