By Nick Hawton
BBC News, Belgrade
As if on cue, the thunder and lightning burst across the Belgrade skyline as the Referendum Commission announced the result of the landmark vote.
The vote marks a significant moment in modern Serb history
A majority of the entire electorate of Serbia, around 3.4 million people, had voted to accept the country's first new constitution since the days of the former leader, Slobodan Milosevic.
"This is a moment for Serbia to rejoice," said the Prime Minister, Vojislav Kostunica.
"It is an historic moment, the start of a new period in the development of Serbia," he said.
In a rare share of unity, all the main political parties had backed the draft constitution.
Even the head of Serbia's Christian Orthodox Church, 92-year-old Patriarch Pavle cast his ballot, the first time he had voted in his life.
Serbian President Boris Tadic said the result showed the citizens supported a "European Serbia".
"We have accomplished one task. But we shouldn't celebrate too much. We have a lot of things to do tomorrow," said Mr Tadic.
One immediate task for tomorrow is the issue of Kosovo, something that has hung over the referendum campaign from the start.
Serbs living in Kosovo turned out in large numbers to support the new constitution.
Some celebrated in the streets when the preliminary results were announced, waving Serbian flags and chanting: "Kosovo, we won't give you up." But the future is uncertain.
Kosovo is officially a part of Serbia but has been run by the UN since the war ended in 1999.
The vast majority of the population are Kosovo Albanians who are demanding independence from Serbia. Serbs want the province to remain a part of Serbia.
In perhaps the new constitution's most controversial part, the text proclaims the province to be an "integral part of the territory of Serbia".
Albanian political leaders have said the constitutional referendum in Serbia was irrelevant for their future.
The international community has said it wants a long-term solution to the Kosovo problem by the end of this year.
But the Serb and Albanian sides seem unlikely to reach agreement and a decision may be imposed by the international community.
One of the key reasons why this new draft constitution has been rushed through - and why a general election is likely to be called in the near future - is because Serbia's fragile government wants to be re-elected before a decision is made on the province's future.
Serb political leaders sense that Kosovo will be granted some form of independence. Any government which is in power in Belgrade if and when Kosovo gains independence could suffer an electoral backlash.
A settlement for Kosovo's future remains elusive
The parties in power want to be re-elected for a four-year mandate before any such decision is made.
Opposition groups accused the government of rushing through the text of the constitution without sufficient consultation. There were also allegations of ballot-rigging in the immediate aftermath of the vote.
The Serbian Parliament will officially proclaim the constitution in the next few days. There is then expected to be a general election either at the end of the year or the start of 2007.
Not much more than 50% of the Serbian electorate decided to take part in this constitutional referendum - a sign of the continuing apathy and disillusionment which afflicts political life here.
But in other ways this does mark a significant moment in modern Serbian history - finally updating the constitution that had been in use since the days of Slobodan Milosevic.