WASHINGTON (Reuters) -WhatsApp said Friday it discovered an advanced cyberespionage effort that took advantage of a chain of security vulnerabilities in the app and Apple devices to hack them.

A researcher with Amnesty International said unidentified members of civic groups appeared to be among those impacted.

In a brief statement, the Meta Platforms-owned communications service said it had patched the security vulnerability that allowed hackers to take advantage of a second vulnerability on Apple devices and hijack the machines. In a statement, WhatsApp said that fewer than 200 users worldwide had potentially been impacted.

Donncha O Cearbhaill, who heads Amnesty's Security Lab, told Reuters that his group was starting to collect forensic data from potential victims.

In a post on X, he said that initial signs were that the hacking "was impacting both iPhone and Android users, civil society individuals among them." He said other apps beyond WhatsApp may also have been affected.