Substantiating an unconfirmed Monday report, Google announced on Thursday that it is expanding its phone offerings with the forthcoming takeover of Gizmo5 – a company that manufactures software which allows users to place voice-over-IP (VOIP) telephone calls via their computers and mobile phones.

Talking about the Google-Gizmo5 deal, Google Voice product managers Wesley Chan and Craig Walker said in a blog post that while the existing users of Gizmo5 can continue to use the service, new signups for the service have been suspended for now.

Chan and Walker elaborated: “While we don't have any specific features to announce right now, Gizmo5's engineers will be joining the Google Voice team to continue improving the Google Voice and Gizmo5 experience. Current Gizmo5 users will still be able to use the service, though we will be suspending new signups for the time being, and existing users will no longer be able to sign up for a call-in number.”

The acquisition of the Internet-based calling service Gizmo5, which is similar to Skype, follows Google’s two-year-back purchase of Grand Central - the service, now called Google Voice, for which it stared accepting new customers only recently.

Having announced the $750-million acquisition of mobile advertising network AdMob on Monday, the Gizmo5 takeover marks Google’s fourth acquisition in 2009 - the Internet search giant acquired video company On2 Technologies in August; and anti-spam security firm reCAPTCHA in September.