Based on votes counted one hour after ballots closed, Merkel's party would win 304 out of 606 seats in the lower house of parliament, ZDF public television reported on Sunday.
ARD TV results also pointed to a narrow absolute majority.
Merkel urged her party to celebrate "a super result" after exit polls suggested she was set to win a third term as German chancellor.
But Merkel's preferred coalition is at risk, as her Free Democrat partners appear not have secured the 5% needed to enter parliament.
She may, therefore, be forced to seek a grand coalition with the Social Democrats - estimated to have won 26%.
SHI/SHI