Police raided the headquarters of the Yugoslav student-based resistance movement Otpor yesterday, snatching computers, equipment and information weeks before crucial elections on September 24th.
Officers swooped on the movement's bases in Belgrade, Novi Sad and Mladenovac in a move that key activist Mr Slobodan Homen described as "totally unconstitutional". He said the police had no warrants and that activists would discuss their next move overnight.
Several hours' drive from the capital, the leading opposition challenger to President Slobodan Milosevic was taking his campaign to the heart of the hardline strongholds of the ruling regime.
More than a thousand people greeted Dr Vojislav Kostunica with cheers when he arrived in Loznica in western Serbia, bang on the border with Republika Srpska, Bosnia - and home to many paramilitaries, active during the war and afterwards.
He told them: "I didn't invite you here to fight. I invite you to elections. Elections should bring us peace - and peace in Serbia."
Loznica sits on the Drina River and its population of 100,000 includes 30,000 refugees from Republika Srpska. Many Bosnian Serbs have also made their homes in Loznica.
Dr Kostunica told the audience he wanted to make Serbia a normal country and a normal state. And he played to nationalist themes, telling the crowd: "I say normal state around the River Drina because this river has started to divide us.
"This river was a bridge to the people but now it is dividing them. And he criticised the regime for its wars: "They divided everything. They destroyed everything that they could and we have to stop it."
On Sunday Dr Kostunica took his campaign to the eastern border town of Zajecar, where thousands turned out. But the real Milosevic supporters are away up rutted roads and in isolated villages, where the daily news comes from state television and many do not read newspapers.
The three hundred villagers of Gornji Bela Reka (Upper white river) live 30 km from Zajeca, close to the Serbian-Bulgarian border. Mr Milivoje Veljkovic (58), is a peasant farmer there.
"Milosevic is with the people," he says. "He has shown it. Ever since he came into power he has fought for Serbia and Yugoslavia. Milosevic has looked after people. Everyone has a pension. I think everyone in the village thinks the same as me," he says.
And on the way to a nearby village, an elderly woman in the black of mourning sits on a stone and watches her two goats. "What do we expect from elections? Who has been up to now will stay." With her pension of less than 700 dinars (£10) a month, she survives with her two goats, three sheep and a small plot of land. "Yes, I will vote for Milosevic," she says.