3-way calling using REFER

I am trying to setup Asterisk to accept REFER requests from softphone (kphone, linphone etc.). On receipt of REFER with refer-to:sipuri, Asterisk should invite the referred entity. This way, one user can refer other 2 users and establish a 3-way call.

Another requirement would be for Asterisk to perform media-mixing for all the users involved in conference.

Does any body know if this would be possible with Asterisk? (Any extra configurations, modules?)

Thanks for you help!!