Country music star Blake Shelton shocked fans in Arkansas with a tweet that he was going to play a free, impromptu show in Fort Smith.

He made the announcement around noon on Thursday, saying he would be playing a show at The Sound Room at 8 p.m.

The concert will only be for people 21 and over and since the venue has limited space it will be first-come, first-serve.

Fans were already lining up for the show less than an hour later.