US-based Akamai Technologies says the smartphones and tablets from more than 100 countries with the Android mobile operating system were hacked for the attacks.

Akamai says the handsets were remotely controlled and targeted companies and institutions without the knowledge of their owners.

The firm says the first attacks took place in early August, and became full-scale in mid-August. They disrupted online transactions at more than 50 firms in the US, Europe and Asia.

The hackers spread virus-infected smartphone applications through Google's official website, most often free-of-charge. About 300 such applications, including video players, have been confirmed so far.

Google deleted the fraudulent apps, which are reportedly indistinguishable from normal ones.

Akamai official Kazuhiro Nakanishi calls the cyberattack a new way to abuse smartphones, which are constantly connected to the Internet.

He says the communication volume of a single handset may be small, but remotely controlling them worldwide resulted in large-scale cyberattacks.