Anier, who counts Motherwell and Dundee United among his former clubs, signs a contract until the end of the season. The Estonian international’s deal with Swedish side Kalmar FF had expired, his last appearance for the Allsvenskan outfit coming at the end of October.
However, the 26-year-old was involved in his country’s 8-1 defeat to Belgium in November, scoring the consolation.
Anier is Richie Foran’s second January signing, following the addition of Dean Ebbe, a striker recruited from amateur football in the Republic of Ireland.
Both players have options in their contract which could see them extend their stay in the Highland capital beyond the summer.
The Ladbrokes Premiership’s bottom side have also agreed an extension to Larnell Cole’s loan deal from Fulham, while David Raven has signed a six-month deal which will keep him at the Caledonian Stadium until January 2018.