The Serbian opposition is contemplating the next move in its campaign to oust President Slobodan Milosevic after the big anti-government demonstration in Belgrade on Thursday.

More than 100,000 people filled the streets and the park around the Yugoslav federal parliament, the body which elected Mr Milosevic two years ago, to call for his resignation.

At the rally, the leader of the Alliance for Change, Zoran Djindjic, gave President Milosevic and his government an ultimatum to step down within two weeks.

''Unless they do so, daily protests will begin in 50 towns and cities in Serbia,'' Mr Djindjic said, to loud cheers.

Road blockades

The campaign of civil disobedience he outlined would involve road blockades in an effort to bring the country to a standstill.

Opponents of Milosevic are planning their next move

This would be an ambitious task: the opposition is launching a challenge to itself as much as to the authorities.

The strategy of the Serbian Government seems to be to ignore the opposition in the hope that it will fade away.

State-run television mentioned the rally only at the end of its news bulletin on Thursday night, dismissing it as ''a failure by all accounts''.

Rally underlined divisions

Showing pictures of the fringes of the demonstration, the television claimed that only 25,000 people turned up.

It poured scorn on the organisers of the rally, accusing them of acting on the orders of the United States and Nato.

The opposition claimed the demonstration as a triumph. But in many ways, events of the evening simply underlined the divisions between its different leaders.

Vuk Draskovic stole the show

The main axis of rivalry is between Mr Djindjic and the charismatic and mercurial leader of the Serbian Renewal Movement, Vuk Draskovic.

Demand for change

Mr Draskovic wants to work within the existing system, which would involve political cohabitation, for a time at least, with President Milosevic.

Mr Djindjic however demands fundamental change in Serbia, starting at the top.

Studio B, the Belgrade television station controlled by Mr Draskovic, did not give live coverage to Thursday night's rally.

But following Mr Draskovic's dramatic and unscheduled appearance on stage, the television aired a special broadcast about the demonstration, devoting most of it to his speech.

Boos and hisses

Mr Draskovic had planned to stay away from the rally and was reportedly viewing it from a vantage point at Belgrade city hall.

But when he saw the size of the crowd, it seems that he decided to appear after all, for fear of leaving the floor open to Mr Djindjic.

Mr Draskovic's electrifying address provoked a mixed response. While part of the crowd was ecstatic, there were also boos and hisses.

At one point, Mr Draskovic's microphone went dead, prompting allegations that his rivals had cut the power.

Back-stage scuffles

''For some, the ousting of Draskovic is more important than that of Milosevic,'' Studio B commented, curtly.

There were back-stage scuffles between Mr Draskovic's bodyguards and Mr Djindjic's security team, and some leaders may feel that they were upstaged by Mr Draskovic.

His speech was the incontestable high point of the evening, and the crowds started to melt away as soon as he finished.

The challenge facing the opposition now is how to harness the energy that clearly exists in Serbia.

After 10 years of war, crisis and international isolation, a growing number of people want Mr Milosevic to leave and they do not care which politicians run the campaign against him.