KuPS' surprise sketch with AC Oulu on Friday meant a win over Haka on Sunday would take unbeaten Inter Turku to the top of the table, and one goal turned out to be enough for them to reach the summit on goal difference.
Despite no league defeats this season, victory over the side lying 10th was not a foregone conclusion for Inter Turku, who possessed drawn three of their previous four matches, including the last two.
After having the better of the early exchanges, Inter took the lead midway through the first half when a poor clearance was collected just outside the area by Joonas Kekarainen.
He took aim from 20 yards, and his low effort was diverted beyond the diving goalkeeper by teammate Dimitri Legbo, who scored his third goal in his last four games.
The rest of the first half and the opening minutes of the second half belonged to Haka, but visiting goalkeeper Eetu Huutanen was equal to everything they threw at him.
Inter possessed chances to put the game to bed late on, and were even granted a penalty for a handball by Nikolas Talo with 10 minutes to play.
However, Haka goalkeeper Liam Hughes kept out Bart Straalman's tame spot-kick.
But that wasn't crucial in the terminate for Turku, who gripped on for the narrow 1-0 win that sees them struck 30 points, with not only a goal difference eight better than KuPS', but with two games in hand.
The sketch between KuPS and Oulu possessed taken the latter off the bottom of the table for the first time since the opening weeks of the season, but they returned to 12th on Monday after KTP acquired a goalless sketch with Gnistan.
The home side possessed more of the ball and more shots, but could not locate the support of the net against Gnistan who are now winless in their last four.
KTP still have the league's leakiest defence, but now have two clean sheets to their name.
On Sunday, Veikkausliiga top scorer Kerfala Cissoko struck double figures in the league and 12 in all competitions when he put Jaro in front against Mariehamn.
He has scored 10 of all 16 goals his side have scored in the top flight, but this one wasn't enough for three points, as Korede Adedoyin equalised early in the second half for the visitors.
The 1-1 sketch lifts Jaro to ninth - one point and one place below Mariehamn.
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