Tens of thousands of demonstrators converged on Berlin on Sunday to protest against Germany's conservatives' norm-shattering overtures toward the far-right.
Police said at least some 20,000 people had gathered just after the protest's 3:45 pm (14:45 GMT) kick-off time outside the Bundestag, Germany's parliament building.
But with demonstrators carrying placards and banners denouncing the conservative Christian Democratic Union (CDU) party arriving "from every direction", a police spokeswoman said that tally "could rise considerably".
Organizers planned to march towards the headquarters of the CDU, whose seeking of the far-right AfD's support for an anti-immigration bill in parliament last week sparked the demonstration less than a month ahead of a snap federal election.
Since the end of World War II, German parties have had an unwritten agreement not to work with the far-right at the national level.
But CDU chief Friedrich Merz, frontrunner ahead of the February 23 election, broke that so-called "firewall" by canvassing for the support of the far-right Alternative for Germany (AfD).
The two parties successfully passed a non-binding resolution on Wednesday in an attempt to block undocumented foreigners at the border, including asylum seekers.
On Friday, they failed to pass another contentious bill to further restrict immigration.
Merz launched his all-out immigration crackdown after police arrested an Afghan man following a deadly knife attack a week ago against a group of kindergarten children.
He "wants to cut through" the norm of not working with "right-wing extremists in one fell swoop", said left-wing NGO Campact, one of the organizers of protests in Berlin.
On Saturday, more than 220,000 people already marched in cities across the country, including Hamburg, Leipzig, Cologne or Stuttgart, according to figures compiled by public broadcaster ARD.
Many trade unions, civil society and human rights groups, churches and environmental activists have answered the call.
Center-left Chancellor Olaf Scholz has warned that the conservatives and the far-right could soon join forces to govern the country, as has been the case in other countries.
