KABUL, April 18 (Reuters) - At least 20 officials working at Afghan President Ashraf Ghani’s palace have tested positive for coronavirus, prompting the 70-year-old leader to limit most of his contact with staff to digital communication, government sources said on Saturday.

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.

“Some of the employees were still working in their offices when the results came out, and we had to quarantine them and their families, but the numbers could be higher,” the official added.

Sediq Sediqqi, Ghani’s spokesman, said the Civil Service Commission has already asked government employees to stay at home before the tests were conducted and that order has been extended for another three weeks.

A government source told Reuters that Ghani, who in the past has said he suffers from health issues related to his stomach, has limited contact with staff, conducting most meetings through video conference calls and meeting only a handful in his inner circle in person.

COVID-19, the disease caused by the new coronavirus has been known to disproportionately affect older people and result in much higher mortality rates within that demographic.

Afghanistan - already battling shortages of food and medicine while violent clashes with the Taliban continue - had recorded 933 positive cases of coronavirus as of Saturday.

Thirty people have died of the virus but health officials say the number of cases are likely to be much higher than reported due to limited testing.

The Afghan health ministry has warned that unless containment measures are improved throughout the war-torn country, Afghanistan is heading for a catastrophe and millions would be infected. (Reporting by Hamid Shalizi, additional reporting by Rupam Jain; Editing by Charlotte Greenfield and Ros Russell)