India on Thursday sought an explanation from WhatsApp over a cyber-espionage scandal days after the Facebook-owned messaging service lodged a lawsuit in the U.S. against an Israeli tech and surveillance firm, accusing it of aiding governments snoop on hundreds of journalists and activists worldwide, including those from the South Asian country.

"Government of India is concerned at the breach of privacy of citizens of India on the messaging platform WhatsApp. We have asked WhatsApp to explain the kind of breach and what it is doing to safeguard the privacy of millions of Indian citizens," Ravi Shankar Prasad, India's Communications, Electronics and Information Technology Minister, said in a tweet.

"Gov't is committed to protecting privacy of all Indian citizens. Gov't agencies have a well-established protocol for interception, which includes sanction and supervision from highly ranked officials in central & state governments, for clear stated reasons in national interest," Prasad added, denying opposition's charges of complicity in the scandal.

WhatsApp, meanwhile, said it had no comment on Prasad's tweet, but referred to a previous statement that the company believes people have the fundamental right to privacy and no one else should have access to their private conversations.

Indian Express newspaper reported Thursday that WhatsApp, in a startling revelation, admitted that journalists and human rights activists in India have been targets of surveillance by operators using the Pegasus spyware, developed by Israel's NSO Group which also goes by the name Q Cyber Technologies.

"Indian journalists and human rights activists have been the target of surveillance and while I cannot reveal their identities and the exact number, I can say that it is not an insignificant number," an unnamed WhatsApp spokesperson was quoted as saying by the Express.

The revelation came after WhatsApp on Tuesday sued the NSO Group, accusing it of helping government spies break into the phones of around 1,400 users of the hugely popular messaging platform, including journalists, diplomats, political dissidents, human right activists and government officials worldwide.

Describing NSO's use of spyware as "an unmistakable pattern of abuse," the lawsuit, filed in a federal court in San Francisco, charged the Israeli firm of facilitating government hacking sprees in 20 countries but identified only three – Mexico, the United Arab Emirates and Bahrain – in the document.

NSO has denied the allegations. "In the strongest possible terms, we dispute today's allegations and will vigorously fight them," the Israeli firm said in a statement. The sole purpose of NSO is to provide technology to licensed government intelligence and law enforcement agencies to help them fight terrorism and serious crime."

India is WhatsApp's biggest market with over 400 million active users.

Although WhatsApp didn't reveal the exact number of targets in India, the Express reported that the messaging platform "contacted and alerted" at least two dozen academics, lawyers, activists and journalists across India that their phones had been under "state-of-the-art surveillance for a two-week period until May 2019."

Sidhant Sibal, a New Delhi-based journalist, corroborated the Express report. Sibal told Reuters the University of Toronto's Citizen Lab – which investigates digital espionage among other research projects - called him about a month ago, informing him that his WhatsApp account was one of several under surveillance.

Earlier this week, he received a text message from WhatsApp, saying the company cared about "your privacy and security."

"In May we stopped an attack where an advanced cyber actor exploited our video calling to install malware on user devices," the company said, explaining why it was writing to Sibal and other affected users like him. "There's a possibility this phone number was impacted, and we want to make sure you know how to keep your mobile phone secure."

Citizen Lab in a post on its website dated October 29 claimed it was helping WhatsApp investigate the incident and would continue to contact "individuals targeted with these attacks to assist them in becoming more secure, and to better understand the cases."

India's opposition and activists have accused the federal government led by Prime Minister Narendra Modi's Bharatiya Janata Party (BJP) of invading citizens' privacy and of curbing dissent. The government has denied the accusations.

Despite New Delhi raising the matter with WhatsApp, opposition leaders targeted the federal government for snooping on its own citizens.

"The Govt seeking WhatsApp's response on who bought Pegasus to spy on Indian citizens, is like Modi asking Dassault who made money on the sale of RAFALE jets to India!," Rahul Gandhi, the leader of main opposition Indian National Congress party, tweeted drawing parallel with another political controversy related to India's purchase of Rafale multirole fighter aircraft manufactured by France's Dassault Aviation.

(With input from agencies)