Most of the 80,000 who attended the conference were Indonesian

The Islamist group Hizb ut-Tahrir - which organised the conference - said it had been the largest gathering of Muslim activists from around the world.

However, the group is illegal in many countries and key speakers have been stopped from entering Indonesia.

A caliphate - or single state for Muslims - last existed in 1924.

Hizb ut-Tahrir regards this as the ideal form of government, because it follows what it believes are the laws of God as set out in the Koran, rather than laws designed by man.

The group says it seeks to set up a caliphate by non-violent means - but many experts see it as ideologically close to jihadist groups.

It is banned in most of the Middle East and parts of Europe.

HIZB UT-TAHRIR Founded in the 1950s by Palestinian jurist Taqiuddin an-Nabhani Active across the Middle East, central and south-east Asia and, increasingly, Europe Seeks a caliphate, or single state, across the Muslim world Banned in most Middle-Eastern countries

Q&A: Hizb ut-Tahrir

If the audience turnout was impressive, not so the speakers lined up to address the crowd, our correspondent adds.

One by one, over the past few days, seven of the delegates invited to speak have dropped out.

Barred

Controversial Indonesian cleric Abu Bakar Ba'asyir was asked to stay away on security grounds, while three national leaders cancelled at the last minute.

The Palestinian delegate was unable to leave the Palestinian Territories, and representatives from Britain and Australia landed in Jakarta on Friday but were refused permission to enter the country.

Hizb ut-Tahrir's spokesman in Indonesia said he was disappointed about these problems and said that the Indonesian authorities had not told the group why its speakers had been barred.

Key speakers were barred from travelling to Indonesia

Hizb ut-Tahrir - or Liberation Party - was founded in Jerusalem in the 1950s by Palestinian religious scholar Taqiuddin an-Nabhani.

Today it has a mainly clandestine following in the Middle East, a large presence in Central Asia - where hundreds of its members have been jailed - and active supporters in the West, including London, which is believed to be one of its main bases.

Many experts see it as ideologically close to jihadist groups, and suspect its commitment to peaceful means is purely tactical.