Germany's center-left opposition has won a razor-thin victory in a regional election that is seen as a test for Chancellor Angela Merkel eight months before nationwide legislative elections.

The opposition Social Democrats and Greens won a one-seat majority over Ms. Merkel's center-right coalition in Sunday's election in Lower Saxony state.

Ms. Merkel described the defeat as 'painful'.

“I am not going to pretend, after all the feelings generated by this election, defeat hurts even more. We are all sad today. Sad that it did not work.''

The election is the last test before September, when polls for Bavaria will take place followed by national elections, which will determine whether Ms. Merkel will win a third term.