The BBC's David Willis, Kuala Lumpur: Movernt set up to fight injustice and "rape of democracy"

But the 18 parties and organisations, calling themselves the Coalition for People's Democracy, had to put off their inaugural meeting after police ordered the hotel where it was to be held to cancel the booking.

"The government is sensitive to the latest developments and pressured the hotel management to refuse the use of the hall," said Tien Chua, spokesman for the coalition.

The group announced a 10-point joint declaration which demands the rights to freedom of speech and assembly, and to a fair trial and impartial hearing in a public court of law.

It also wants the abolishment of the Internal Security Act, under which the former deputy prime minister, Anwar Ibrahim, and 16 of his associates have been jailed without trial.

Although there are no immediate plans to launch a direct challenge to the government, one of the leaders said the new movement could develop into a single political force.

Anwar's arrest has escalated the protests

They said it was borne out of the grave political economic and social crisis currently affecting Malaysia, including the detention of Mr Anwar.

Since his arrest a week ago, they have staged a number of demonstrations which have been broken up by the police.

Merdeka Square sealed off

Earlier on Sunday, riot police sealed off the main square in Kuala Lumpur, to prevent a repeat of last Sunday's demonstration against the Prime Minister, Mahathir Mohamad.

BBC Correspondent in Kuala Lumpur David Willis reports on a day of unrest

Several thousand supporters of Mr Anwar clashed with the police when they tried to march on the Merdeka Square again on Saturday.

Police used water cannon to break up the rally and some arrests were made.

Mr Anwar has not been allowed to see his lawyer or his family. Complaints about his treatment have been made to the Malaysian government by the United States, Australia and the UK.

Prime Minister Mahathir has expressed concern that foreign countries could impose sanctions in response to the arrest.

On Friday, the prime minister said Mr Anwar would be brought to court only when the protests stopped.

Lawyers for Mr Anwar, who was arrested on suspicion of sexual misconduct and inciting public unrest, say they still do not know what charges he is likely to face.