Sister Elisabeth and Sister Irmgard (L) cast their votes at the polling station where German Chancellor and Christian Democratic Union (CDU) leader Angela Merkel is expected to cast her vote for the German general election (Bundestagswahl) in Berlin, September 22, 2013. [Photo/Agencies]

BERLIN - Germans started to cast their ballots for a new parliament early Sunday, in an election that will decide who will rule the country for the next four years.

Some 61.8 million voters were called to go to ballot boxes, and 34 parties will run in the election of Bundestag, lower house of the German parliament.

A total of about 80,000 polling stations opened at 8:00 am (0700 GMT), while another 10,000 stations will receive postal voting until 6:00 pm. (1700 GMT).

The ruling coalition consisting of Chancellor Angela Merkel's conservative Christian Democratic Union (CDU), its Bavarian sister party Christian Social Union (CSU) and the pro-business Free Democratic Party (FDP) faces challenges from another major party, the center-left Social Democrats (SPD) and its preferred partner, the Greens.

In recent polls, the CDU/CSU union was in a leading position, but its partner, the FDP, was wiggling around the 5-percent threshold to enter parliament.

In Sunday's election, each voter could cast two votes -- the first for a constituency candidate to represent his/her constituency in parliament, and the second for a party.

Half of the 598 parliament seats would be decided by the first votes, while each party's overall seats in parliament would be allocated according to the share of the second votes obtained.

A ruling party or coalition needs a majority of seats in the legislature.

Exit polls results by research institutes are expected to be published shortly after the close of ballot stations at 6:00 pm (1700 GMT). An official provisional result is scheduled to be released early Monday.