The chaos at the conference reflected the tensions within the unity government set up between President Robert Mugabe and old rival Morgan Tsvangirai in February to try to end political paralysis and reverse a decade of economic decline.

Trouble broke out between the delegates from Tsvangirai’s Movement for Democratic Change (MDC) and Mugabe’s ZANU-PF during an opening statement by the speaker of parliament.

Riot police drove them out of the conference venue.

The conference was mired in controversy and administrative glitches from the start. Some delegates could not be accredited on Sunday night and slept in the open, raising tempers even before official proceedings started.

The conference, which was initially scheduled to be opened by Mugabe, with Tsvangirai also expected to attend, was running about four hours late on Monday as officials battled to accredit the 4,000 delegates who had been invited.

When Zimbabwe speaker of the lower House of Assembly, Lovemore Moyo, from Tsvangirai’s MDC, got up to deliver his opening speech, he was drowned out by youths singing revolutionary songs and delegates heckling each other.

There was no immediate explanation as to why Mugabe and Tsvangirai had not turned up for the conference, part of a process which should lead to the adoption of a new national constitution and fresh elections in about two years.