The Delhi Police has reported a breach of computers at the National Informatics Centre (NIC), in Delhi, in which data relating to national security and VVIPs like Prime Minister Narendra Modi were compromised early this month.
Police sources said the computers affected also stored data relating to National Security Advisor Ajit Doval, Indian citizens and senior government functionaries.
The NIC is tasked with setting up and maintaining secure information and communication technology for the government.
Delhi Police's Special Cell filed a case based on a complaint filed by an NIC employee immediately after the attack.
According to sources, the attack began with the receipt of an e-mail. When the employee clicked on attachments in that mail, data stored on that machine became compromised and other computers were affected.
The email was traced to an IT company in Bengaluru.
However, according to news agency ANI the email was sent from the United States via a proxy server to the Bengaluru-based firm.
Sources said further investigations are going on.
The breach comes amid allegations a Chinese firm - Zhenhua Data Information - conducting covert surveillance on thousands of Indians, including the prime minister, the President, the Vice President and the Army Chief.
Sources said the government has constituted an expert committee under the National Cyber Security Coordinator to study these breaches. The committee is to submit a report within 30 days.
The issue has also been raised by the external affairs ministry with Sun Weidong, the Chinese ambassador to India. The Chinese government has said Zhenhua is a privately-owned company with no links to Beijing.
The row over alleged snooping and surveillance by Chinese firms comes amid a serious military stand-off between the two countries along the LAC (Line of Actual Control) in Ladakh.
Tensions have spiked since a violent confrontation in the Galwan region in June, in which 20 Indian soldiers were killed in the line of duty.