The actor James McAvoy has donated £275,000 to a crowdfunding campaign set up to by a group of doctors to raise money to buy vital protective equipment for NHS staff treating coronavirus.

The Scottish star of the X-Men movies and Atonement gave the money to support the efforts of concerned NHS medics who launched a page on Thursday appealing for money to buy personal protective equipment (PPE) such as masks, visors and gloves because they feel they are “going to war without armour and protection”.

The campaign has raised more than £440,000, surpassing the initial target of £200,000, which has now been extended to £500,000.

One of the medics behind the project, Dr Salaj Masand, said: “We are overwhelmed and speechless at the trust and faith people have put into us to deliver this. The number of very generous donations from everyone doubled our target within three days.”

McAvoy’s donation was “mindblowing”, he said, and would mean an order for 75,000 masks and 75,000 visors can be placed immediately rather than having to wait for enough donations to filter through.

“This is a global catastrophic event and an extremely tough time for governments across world, no different from ours. There is a worldwide shortage of PPE [that’s] likely to go on for months,” he said. “The government is doing all it can but the NHS needs all the help it can get. We are also competing with the commercial market who are trying to sell the same PPE for extraordinary prices.”

He said the situation was urgent and that time was of the essence, noting that one of the doctors behind the crowdfunding campaign has tested positive for coronavirus. The campaign was working with the government, which had been inundated with offers of inadequate equipment at inflated prices from private companies.

“That is why we raised the capital ourselves and hope to help government distribute these supplies in best possible way,” he said.

The doctors say in their appeal: “Unfortunately current hospital supplies are not sufficient and while we are reassured the government is doing everything it can, healthcare workers on the frontline are risking themselves daily without adequate protection to care for sick patients. Healthcare workers on the frontline without PPE is the equivalent of going to war without armour and protection.”

McAvoy said on Instagram: “Money donated today will save lives … Help us to help the government to help the NHS.”

The Guardian revealed on Friday that the Department of Health had rejected high-level medical advice about providing NHS staff with certain protective equipment during an influenza pandemic because stockpiling it would be too expensive.

Documents show that officials working under the then health secretary, Jeremy Hunt, told medical advisers three years ago to reconsider a formal recommendation that eye protection should be provided to all healthcare professionals who have close contact with pandemic flu patients.