Hearts, meanwhile, suffer their first defeat of the campaign
Karela United ended Hearts of Oak's unbeaten start to the Ghana Premier League season with a deserved 1-0 victory at the Aliu Mahama Sports Stadium in Tamale on Saturday.
Mohammed Zaidan struck in the 88th minute to settle a closely contested Matchday Four encounter and give Karela a much-needed three points in front of their home supporters.
Karela started with greater purpose and created the better opportunities during the first half, but their dominance was not reflected on the scoreboard as they struggled to find the finishing touch.
Hearts of Oak also had opportunities of their own, but the Phobians failed to create the same level of danger as their hosts, with neither side able to break the deadlock before the interval.
Karela continued to push after the restart and remained patient despite their failure to convert their earlier chances. Their persistence finally paid off late in the game.
With two minutes of normal time remaining, Zaidan found himself unmarked as a low, drilled ball came into his path. He reacted quickly to poke the ball past Hearts goalkeeper Sharif Shuaib, who was deputising for captain Benjamin Asare while he is away with the Black Stars.
Shuaib had made several important saves to keep Hearts in the game, but he was rooted to the spot as Zaidan's effort found the back of the net.
The goal sparked celebrations in Tamale as Karela held on through the closing stages to secure a valuable victory and bring an end to Hearts' unbeaten run.
The result is a major boost for Karela, who had entered the game looking to respond after their stoppage-time defeat to Aduana FC last weekend.
Hearts, meanwhile, suffer their first defeat of the campaign after opening the season with two wins and a draw. The Phobians could also surrender top spot by the end of the weekend, depending on results elsewhere.
Karela will now turn their attention to another difficult assignment against Asante Kotoko away in Kumasi, while Hearts of Oak will look to bounce back when they face Dreams FC in their next league fixture.