A plan to build the UK's biggest mosque in Stratford, east London, has been rejected by councillors.
Thousands of supporters gathered outside Newham Council's town hall ahead of the decision.
The huge mosque would have been four times the capacity of St Paul's Cathedral with room for almost 10,000 worshippers.
The Islamic missionary group Tablighi Jamaat has been trying for 10 years to build a mosque in Newham.
Supporters outside the town hall, some of whom had come from Birmingham and Bradford, held signs reading: "15 years of waiting. Not a day more. Vote yes to the Riverine Centre".
'Extremely let down'
BBC London reporter Alex Bushill estimated that 3,000 people had gathered.
The crowd dispersed after the meeting.
The Abbey Mills Mosque - also known as the Riverine Centre - would have become the biggest Islamic centre in the UK and one of the largest in western Europe.
Council officers recommended councillors refuse permission for expansion on the former industrial land, amid strong opposition and concern about the project.
All eight councillors on the committee voted against the plan at about 20:30 GMT.
Councillor Conor McAuley said it was rejected on the grounds that the land is designated for mixed commercial and residential use, there was not enough consideration for transport and it would not have led to more jobs and homes.
He said: "That really wasn't good enough."
Community leader Ala Uddin Ahmed said: "There are 90,000 Muslims around the borough.
"The Muslim community is growing and there is need for bigger worship.
"We are extremely let down. We think it is unjust because of the demand of the local people and the Muslim community."
Campaigner Alan Craig of the Christian Peoples Alliance had criticised the proposal, saying it would create a "ghetto" or "Islamic enclave".
Some local Muslims had also expressed concerns that it would give one Islamic group too much dominance over the community.
The mosque would have included a prayer hall for up to 7,440 men and a separate facility for almost 2,000 women.
Tablighi Jamaat currently uses part of the 17-acre Abbey Mills site to house a temporary hub which can host up to 2,500 people.
Since Tablighi Jamaat moved into the Abbey Mills site in 1996, it has been involved in a series of application and enforcement disputes with Newham Council.
Tablighi Jamaat currently uses part of the site to house the London Markaz, also referred to as Masjid-e-Ilyas, a temporary hub which can host up to 2,500 people.
The Islamic sect, which started in India in the late 1920s, has been accused in the past of radicalising young Muslims.
The group has said it "refrains from political or controversial activities and stands for democracy and freedom" and that it "promotes social and religious integration".