Watch as Ugandan police fire tear gas into crowd at opposition office

Heavily armed police have surrounded the headquarters of Uganda's main opposition party and fired tear gas from a helicopter to disperse a crowd, raising tensions amid mounting allegations of vote-rigging in elections.

Kizza Besigye, the main rival to President Yoweri Museveni, was holding a meeting with other leaders of his party when police tried to force themselves into the premises in Kampala, said Ingrid Turinawe, an aide to Mr Besigye.