Celtic had a routine 2-0 victory over St Mirren at St Mirren Park with both goals arriving in the opening 12 minutes.
Hearts beat Hibernian 2-0 in the first Edinburgh derby of the season, inflicting a third consecutive defeat on their rivals who remain bottom of the table.
Motherwell ended Dunfermline’s unbeaten start to the campaign with a 4-2 win.
The visitors were three goals to the good early in the second half but the Pars rallied with two goals but Motherwell secured the points with a late fourth goal.
At one stage the hosts St Johnstone led 3-1 but United scored twice late on for a share of the spoils.
United took an early lead only to concede three goals before half-time and with 11 minutes remaining it seemed as if the Saints had wrapped up their first home win of the campaign.
But United struck in the 79th and 83rd minutes to claim an unlikely point.
Inverness enjoyed a 2-1 home success over Kilmarnock to lift themselves off the foot of the table.
Caley Thistle took the lead only for the visitor’s to restore parity before the break.
And that is the way it looked likely to finish until a minute from time when the host’s struck to give themselves their first win of the season.