Hearts thrashed Motherwell 6-0 at Tynecastle on Saturday to close the gap on second-placed Aberdeen to three points.
Igor Rossi, Osman Sow and Gavin Reilly (penalty) scored in the first half and Callum Paterson, Juanma and Arnaud Djoum (penalty) struck in the closing stages as Robbie Neilson's men claimed an emphatic win.
Dundee are into the top six thanks to a 4-2 victory over Partick Thistle at Firhill. Kane Hemmings (penalty), Gary Harkins and Greg Stewart all scored in the first 15 minutes and Harkins struck again after David Amoo pulled one back. The Jags had Liam Lindsay sent off in 77 minutes but Kris Doolan reduced the deficit in the last minute.
Kilmarnock beat Inverness CT 2-1 at Rugby Park to move 14 points clear of bottom club Dundee United. Greg Kiltie's early opener was cancelled out by Ross Draper but Craig Slater got the winner early in the second half.
St Johnstone and Hamilton Accies drew 0-0 at McDiarmid Park.
Ross County host Aberdeen on Sunday, live on Sky Sports at 12.15pm.