By Ray Furlong
Worshippers lucky enough to find a seat fill the pews between the scaffolding, others stand crammed in the doorway.
The current protests involve a broad coalition, as in 1989
Still more are outside on the square, listening to the pastor on a loud speaker system. But this is not a religious revival - it is a political one.
Back in 1989 the Nikolaikirche in Leipzig was the focus for the first protests against communism, with numbers growing steadily until the regime collapsed.
Now, the same man who organised those demonstrations is preaching to mass crowds again, this time against an attack on Iraq.
"The people pushing for war can be stopped," he says, to a surge of applause from the congregation.
In his jeans and denim jacket, Christian Fuhrer does not look like a man of the cloth - but the church in East Germany often attracted rebels.
Word of mouth
In 1989 he held prayer meetings every Monday in which he preached against the regime, followed by a protest march through the city.
"In 1989 the people of Leipzig experienced a miracle, and they learned from it that things which seem impossible can happen," Mr Fuhrer says.
There are no posters advertising the "Montagsdemo" - news has spread by word of mouth.
When Fuhrer started his anti-war sermons shortly before Christmas, only a few dozen people came.
By the beginning of January there were hundreds - and last week there were 25,000.
They are the biggest regular peace protests in Germany. "Leipzig is the capital of the German peace movement," boasted the local Saechsische Zeitung recently.
'Everybody wants peace'
Many of the people who come also took part 14 years ago, among them Sebastian Krumbiegel. Then a student, he is now a well-known pop star in Germany. Easy to spot with his dyed red hair, he is constantly signing autographs as we speak.
"In 1989 there was an enemy, there was the police, and there was fear," he says.
"People were thinking - when are they going to start shooting. Now the police are smiling and helping us, because everybody wants peace.
"This war is so openly about money and power that people feel the need to take to the streets."
The Church service is characterised by a sombreness and quiet dignity. After the sermon, a young man reads a poem. Prayers for peace are said, and a youth choir leads the hymns.
The mood is then taken out onto the streets.
The church revival is political, not religious
While other peace demos have a carnival atmosphere - with drums, whistles and music - the Leipzig march is almost silent as it snakes through the city centre and ends by the Opera House.
Here there are more speeches, and pledges to return next week.
"Leipzigers have a tradition of protesting," says
Andrea, a student who took part as a small child in 1989, "and this is such an important issue."
Not everyone here joined those first protests. The former communist party, the PDS, now has a modest presence, as does the anarchist group Attac.
"In 1989 there was also a very broad coalition of protesters," says Attac member Matthias Berndt.
'Giant peace wave'
"Things were clearer then - everyone wanted freedom of press, freedom of speech, and so on. Now it's different. For instance we want the American bases in Germany closed down, whereas other people don't support this."
As war looms closer, the protests look like they will continue growing.
Christian Fuhrer notes that other towns are now following in Leipzig's footsteps.
"We hope to generate a wave of prayers and protests across Germany, a giant peace wave to prevent a new wave of violence and terror,' he says.
But is this realistic? The peace pastor admits no doubts. "If you don't believe in miracles, you're not a realist."