The opposition in Serbia is gearing up for a summer of anti-government protests which it hopes will climax in mass rallies on the streets of Belgrade.

Their aim is simple but ambitious: to topple the government of President Slobodan Milosevic through the sheer force of popular will.

Over the past two weeks, opposition groups have been organising almost nightly rallies in provincial towns across Serbia, calling on Mr Milosevic to resign.

The demonstrations have brought together people from a broad cross-section of Serbian society: pensioners, army reservists, the unemployed, students.

Opposition leader Zoran Djindjic said: "When the first round of rallies ends, we will embark on the biggest march in the history of the world.

"We will give Milosevic five days until we reach Belgrade, and we will tell him: 'Don't wait for us in Belgrade.'"

Mr Djindjic has emerged as the leader of the Alliance for Change, an umbrella group bringing together about 30 opposition organisations.

'Milosevic must go'

Efforts to topple President Milosevic appear to have been boosted by the decision of the maverick Yugoslav politician, Vuk Draskovic, to take his forces onto the streets.

Mr Draskovic's Serbian Renewal Movement is bigger than the rest of the opposition put together and, crucially, it controls a Belgrade television channel, Studio B.

"I think Serbia must go to the future and the condition for that is that Mr Milosevic, politically, must go to the past," Mr Draskovic told the BBC. His announcement put an end to days of wavering between the government and the opposition.

During the conflict with Nato, Mr Draskovic held the position of Yugoslav deputy prime minister, until he was dismissed for his outspoken criticism of the way President Milosevic was conducting the war.

Economic grievances

The disastrous consequences of the war with Nato have acted as a catalyst for the protest movement. But opposition leaders are drawing on long-standing grievances with the way Serbia has been governed for the past 10 years.

Most of these complaints are economic. Pensioners and army reservists have been demanding outstanding payments - benefits which have declined in real value with the slump of the Yugoslav dinar.

Unemployment has been exacerbated by the closure of factories destroyed by Nato bombs, and many families are now living below the poverty line.

The question now is whether the opposition can forge itself into a credible force to challenge the rule of Mr Milosevic and his ruling Socialists.

The best-attended rally so far, in Leskovac in southern Serbia, was a local initiative without the involvement of the Alliance for Change. And other local activists have expressed disenchantment with the organised opposition parties, accusing them of failing the population of Serbia.

Egos not policies

In the past, the Serbian opposition has disintegrated into internal squabbles and rivalries. There are signs that history could be repeating itself.

Rather than throwing his weight behind the Alliance for Change, Vuk Draskovic appears to be launching a rival movement of street demonstrations.