Hackers used malware through WhatsApp and targeted officials from several countries, including US allies, according to a Reuters report.

The attack, which took place earlier this year, reportedly affected senior government and military figures from at least 20 nations.

WhatsApp, which is owned by Facebook, carried out an investigation and determined that officials were among those the hackers targeted, according to Reuters. Journalists and human rights activists have also claimed to be victims of the attack. This week, WhatsApp sent a notification to users it knows were affected.

Earlier this week, WhatsApp filed a lawsuit against NSO Group, claiming the Israeli developer created hacking software that exploited servers owned by the messaging service. Hackers used that to access the phones of at least 1,400 people, according to the suit.

The victims are said to be in countries including the US, United Arab Emirates, Bahrain, Mexico, Pakistan and India.

NSO says it sells software strictly to governments in order to help them tackle criminals and terrorists.

However, cybersecurity researchers have found NSO products used against a wide range of targets, including protesters in countries under authoritarian rule. An independent research group working with WhatsApp, named CitizenLab, said at least 100 of the victims are journalists and dissidents, not criminals.

Update: The Israeli government on Friday denied any involvement in an alleged cyber- hack by Israeli surveillance firm NSO Group.

Israeli security cabinet minister Zeev Elkin said that if anyone had done anything “forbidden” they could expect to find themselves in court.

“NSO is a private player using capabilities that Israelis have, thousands of people are in the cyber field, but there is no Israeli government involvement here, everyone understands that, this is not about the state of Israel,” Elkin told 102.FM Tel Aviv Radio.

Elkin said “I don’t see any political fallout from this incident.”

He added: “It is true that when people do things that are forbidden - I have no way of determining whether they did indeed do anything forbidden - then the justice system here and in other countries will throw the book at them.

WhatsApp is used by 1.5 billion people monthly and has often touted a high level of security, including end-to-end encrypted messages that cannot be deciphered by WhatsApp or other third parties.