Kris Commons and Scott Brown both scored twice as Premiership champions Celtic beat Aberdeen 5-2 at Parkhead on Saturday.
Anthony Stokes was also on target for Neil Lennon's men, with Niall McGinn and Shaleum Logan netting for the Dons, who qualified for the Europa League.
Motherwell are just a point behind the Dons after beating St Johnstone 2-1 at Fir Park. Stephen McManus got the winning goal after Dave Mackay had cancelled out Lionel Ainsworth's opener.
In the other top-six game, Inverness CT and Dundee United drew 1-1. Ryan Christie gave Caley Thistle an early lead but Farid El Alagui equalised with 20 minutes left.
Gregg Wylde scored a superb late winner as St Mirren took a big step towards safety by beating Ross County 1-0 in Paisley.
Sam Stanton pounced with two minutes remaining to earn Hibernian a 1-1 draw with Partick Thistle at Easter Road after Kris Doolan had scored early on for the Jags. Hibs had Michael Nelson sent off in the 80th minute.
Kilmarnock, who are second from bottom, are away to Hearts on Sunday.
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