"The Speaker will now lead the next steps toward forming a new government. To allow that process to begin immediately, I hereby request to be relieved of my duties as prime minister," Kristersson said in a statement posted on X, Xinhua reported.
Preliminary results released earlier Thursday by the Swedish Election Authority showed that the center-left opposition bloc had secured a parliamentary majority, with all 6,626 electoral districts counted.
Together, the four opposition parties received 49.6 percent of the vote and secured 176 seats in the 349-seat parliament. Kristersson's right-wing bloc received 48.8 percent of the vote and won 173 seats.
The focus now shifts to whether the four opposition parties can agree on a governing arrangement. The grouping brings together the Social Democrats, the Left Party, the Green Party and the Center Party. The Social Democrats remained the largest party, receiving 28 percent of the vote and securing 99 seats.
Reaching such an arrangement could prove difficult given the parties' significant policy differences. Swedish Television domestic political commentator Mats Knutson cited taxation, sick-pay deductions and nuclear power as key areas of disagreement, while noting that compromises could be reached on other issues.