Voters have to be 18 and over to vote in all other 15 German states and in federal elections. Those aged 16 and over are, however, allowed to vote in municipal
elections in seven states.
The election result in Bremen, the smallest of Germany's states, is expected to return the ruling coalition of Social Democrats (SPD) and Greens to power, while Angela Merkel's conservative Christian Democrats are expected to be relegated to third place, according to opinion polls.
But the news could get worse for Merkel. Opinion polls predicted that the Chancellor's allies in the federal government, the pro-business Free Democrats (FDP), may even lose all their seats in the regional assembly.
Initial exit poll results are expected in the early evening.