from the BBC:
...On Monday Mr Mugabe's supporters disrupted the opening speech by dancing and singing revolutionary songs, prompting an angry reaction from supporters of Mr Tsvangirai - his former rival.
Water bottles were thrown, delegates scuffled with each other and riot police were brought in to clear the venue.
Mr Mugabe's Zanu-PF party wants the new constitution to be based on a draft drawn up last year, but critics say it gives the president too much power. ...