Encrypted communications provider Silent Circle this week enabled customers to make secure, outbound landline calls to non-members in 79 countries, a move it claims will cause major disruption to operators and rival OTT players.

In addition, customers can use the service, which is called Out-Circle Calling (OCC), to make calls, send texts and video-chat with mobile phones in 41 countries. Prices start at $12.95 (€9.52) per month. For that, users get their own 10-digit Silent Phone number, 100 minutes of credit, unlimited member-to-member calling and unlimited texts. Customers can also receive calls and messages to their Silent Phone number from anyone in the world. And because it's a VoIP service, there are no roaming fees.

"The facts are that Out-Circle Calling provides a low-cost, private alternative to traditional mobile calling plans that everyone from your neighbour to travelling multinational executives can use," said Mike Janke, CEO of Silent Circle, in a statement on Thursday.

In a separate blog post, Janke took aim specifically at rival Skype, calling it a "wiretap-friendly" communication service.

"Today, Skype is banned from being used in many of the Fortune 1000 companies and shunned by anyone expecting some level of privacy," he claimed.

"I don't necessarily fault [Skype parent] Microsoft, as prior to the summer of [NSA whistleblower] Snowden every major technology company was capitulating on some level to its host-country intelligence service," he continued. "Things are different now. The world now understands that a Skype call is not private."

Silent Circle is also one of the companies behind Blackphone – a privacy-focused smartphone. The phone was developed by SGP Technologies, a joint venture between Silent Circle and handset maker Geeksphone. The handset comes pre-loaded with Silent Circle's encrypted communications services.

Unveiled at Mobile World Congress, Blackphone quickly sold out when it was made available for pre-order. It began shipping last week and SGP plans to put a new batch of Blackphones on sale next week.