Steve Gerrard's men won 3-0 against St Mirren and large groups of supporters ignored coronavirus restrictions to gather outside the stadium prior to kick-off to welcome their heroes amid clouds of pyrotechnics.
Rangers could mathematically seal the title on Monday (AEDT) if Celtic fails to win at Dundee United.
However, the celebrations had already begun as the Rangers squad ran off the field at the full-time whistle to celebrate with supporters outside.
Scotland remains under a national lockdown to curb the spread of COVID-19.
Steven Gerrard's journey into Ibrox Stadium today...— Footy Accumulators (@FootyAccums) March 6, 2021
ENJOY 🇬🇧🇬🇧🇬🇧 pic.twitter.com/xZtKVg5AIV
"We are extremely disappointed supporters have gathered at Ibrox today," a Scottish government spokesperson said.
"At this crucial stage of suppressing the virus, the actions of this minority of individuals jeopardises the safety of other supporters, the police on duty and the wider community.
"We will continue to engage with Police Scotland and the club."
There are fears the scenes could be repeated on Monday (AEDT) if another Celtic slip-up allows Rangers to seal a first major trophy since the club went into liquidation and was forced to restart in the fourth tier of Scottish football in 2012.
In a statement, Police Scotland chief superintendent Mark Sutherland said: "I would remind supporters that in line with current Scottish Government coronavirus guidelines, all gatherings are currently prohibited and we would urge members of the public to comply with these restrictions."
No fans have been allowed into Ibrox all season, but that has not stopped Rangers registering a 100 per cent record, winning all 16 games and conceding just two goals in the process.
Gerrard's men now lead Celtic by 21 points. Even if the Hoops do win on Monday (AEDT), the Gers would only need a point when the two sides meet on 21 March to seal the title at Celtic Park.
St Mirren is the only side to beat the runaway league leader in any competition this season, when it shocked Rangers in the League Cup in December.
However, there was never any doubt about the outcome this time as the hosts raced into a 2-0 lead inside 16 minutes.
Ryan Kent's twisting run and finish opened the scoring before Alfredo Morelos continued his return to form by firing in form a narrow angle.
Ianis Hagi added a third just a minute into the second-half from Kent's low cross.
At the other end of the table, Kilmarnock is bottom after losing a five-goal thriller 3-2 at Ross County.
Victory takes County four points clear of Killie, which is yet to win in five games under new manager Tommy Wright.
Hamilton's 0-0 draw at Aberdeen sees it move up to 11th.
Motherwell eased its relegation fears with a 3-1 win over Livingston to move nine points clear of the bottom two.
St Johnstone backed up its first ever Scottish League Cup win last weekend with a 1-0 win over third-placed Hibernian.