Germany’s anti-immigrant “Alternative for Deutschland” party (AfD) is expected to make huge gains in a key state election on Sunday.

The poll, in the northern state of Mecklenburg-Vorpommern, comes a year after Chancellor Angela Merkel’s decision to open German borders to hundreds of thousands of refugees. And it will be followed by another key vote in Berlin in two weeks and national elections next September.

Voters have already voted in droves for the AfD, rejecting Merkel's Christian Democrats in three state elections in March.