At least 20 officials working at Afghan President Ashraf Ghani's palace have tested positive for the coronavirus, prompting the 70-year-old leader to limit most of his contact with staff to digital communication, government sources said.

An official document delivered to the Presidential Palace in Kabul is thought to have infected staff, many of whom began feeling unwell and were tested earlier this month, according to a senior health official.

“A contaminated document was sent to an office inside the palace from another government department and that's how the employees were infected,” the official told Reuters, speaking on condition of anonymity.