Angela Merkel is on course to secure an historic fourth term as German Chancellor when the country goes to the polls today.

The 63-year-old leader of the Christian Democratic Union (CDU) of Germany party is unlikely to secure a majority in the new parliament but is widely expected to form a coalition.

Merkel told supporters in Berlin on Saturday that they needed to keep up their efforts to sway undecided voters, saying "many make their decision in the final hours".

After handing out coffee and chatting with the campaign workers in Berlin, Mrs Merkel headed north to her own region, walking through the streets of the city of Stralsund shaking hands, posing for photos and signing autographs.

She also campaigned in the northern city of Greifswald and planned a stop as well on the island of Ruegen in the Baltic.

Her main challenger, Social Democrat Martin Schulz, was in western Germany at a rally in the city of Aachen.

"Regardless of how it turns out tomorrow, it was a great and wonderful campaign," Schulz told the cheering crowd, who waved red Social Democratic and blue European flags.

Merkel, a conservative, has governed for the past four years with the centre-left Social Democrats. That "grand coalition" of the biggest parties had a huge parliamentary majority, but the two are traditional rivals and the combination is not popular with the parties' members.

Merkel can hope for a centre-right majority with the pro-business Free Democrats, with whom she ran Germany from 2009 to 2013, or an alliance with the traditionally left-leaning Greens.

If neither combination wins a majority - as recent polls suggest - an alliance of Merkel's conservatives with both the smaller parties could be tried for the first time. The combination is called a "Jamaica" coalition because the parties' colours match those of that country's flag.

Polls suggest Schulz is likely to fall short of a majority for any alliance that would make him chancellor. He could in principle govern with the Free Democrats and Greens, or with the Greens and the Left Party.

German polls also suggest that the far right Alternative for Germany party (AFD) could win up to 60 seats after using anti-immigration rhetoric during the election.

However, the next government will not include the AfD because all other parties say they will not work with it and AfD itself treats what it calls "the old parties" with contempt.

Merkel’s closing campaign rally in Munich was disrupted by right-wing protesters who booed and heckled her for half an hour as she made her speech.

“With whistling and yelling, one will surely not shape Germany’s future,” Merkel told the protesters.

Although Germany's 61.5 million eligible voters will have the opportunity to elect their new parliament on Sunday, a new government is not expected to be in place quickly.

In 2013, Merkel's "grand coalition" took office just before Christmas, around three months after voters had their say. That was a record for post-Second World War Germany, but could be matched or exceeded this time. In the meantime, the existing government stays on a caretaker basis.

Parties may be reluctant to show their cards before an October 15 state election in Lower Saxony, one of Germany's most populous regions. And a coalition deal may need endorsement from members of at least one party. Four years ago, a ballot of the Social Democrats' members accounted for much of the delay.