Germans voted today in a federal election that saw Chancellor Angela Merkel's conservatives come in as the strongest parliamentary group and the far-right Alternative for Germany (AfD) enter parliament for the first time.

Following are highlights of comments and reactions:

Angela Merkel told supporters in Berlin: "Of course we had hoped for a slightly better result. But we mustn't forget that we have just completed an extraordinarily challenging legislative period, so I am happy that we reached the strategic goals of our election campaign," Merkel said.

WATCH: Angela Merkel wins a fourth term as German chancellor

"We are the strongest party, we have the mandate to build the next government - and there cannot be a coalition government built against us," Merkel added.

Martin Schulz, SPD party leader and chancellor candidate, told ZDF broadcaster: "We cannot have an extreme right-wing party leading the opposition in Germany, therefore ... we will go into opposition." He added: "Our role is quite clear: we are the opposition part."

Schulz told supporters in Berlin that this election was a "bitter day" for Germany's Social Democrats, adding: "Especially depressing for all of us is the strength of the AfD, which for the first time brings a right-wing party into German parliament in such a strong position. This is a turning point."

"The fact that we took in more than 1 million refugees in our country is still dividing in our country. What for some has been an act of humanity and charity is to others menacing, strange and filled with fear. We did not manage to persuade all of our voters that Germany is strong enough not to leave anyone behind," Schulz said.

CDU supporters celebrate as exit polls are announced. Photo: Reuters

Horst Seehofer, CSU leader and Bavarian Prime Minister, told broadcaster ARD: "We had a vacuum on the right side that we need to close now. The best way to do that is with policies that ensure that Germany remains Germany and that we have the immigration and security questions under control."

Alexander Dobrindt, a senior CSU member, said: "I believe for everyone in the government this is a bitter election night. But I think it is too early to draw conclusions - like the SPD."

Volker Kauder, parliamentary floor leader of Merkel's conservatives, told ARD television that his party reached its goal to win the election. "We have the mandate to lead the next government," Kauder said.

SPD parliamentary floor leader Thomas Oppermann told broadcaster ARD: "We must of course accept voters' choice, they (AfD) are a party in parliament now... But I will say very clearly that if there are any racist tones in this parliament, we will object to them, very clearly."

Wolfgang Kubicki, FDP deputy party leader, told broadcaster ARD: "You cannot force the Greens and us into a coalition just because the SPD bows out."

SPD deputy party leader Manuela Schwesig told ZDF broadcaster: "That is a really bad result for the SPD. That is a heavy defeat... For us, the grand coalition ends today. For us it's clear that we'll go into opposition as demanded by the voter."

SPD parliamentary floor leader Thomas Oppermann told broadcaster ARD, when asked whether Schulz would remain party head: "Martin Schulz started the renewal process of the SPD at the party meeting in March, and he will continue that renewal. We win together and we lose together."

AfD top candidate Alexander Gauland said: "The government, whatever it will look like, should get ready for tough times. We'll chase them. We'll take back our country and our people."