Ethnic Indian protesters in Malaysia are calling for reparations from the UK for sending Indians to Malaysia as indentured labourers a century ago.
Riot police were dispatched to the British High Commission in Malaysia's capital, Kuala Lumpur to disperse the rally.
The Malaysian authorities had banned the event, despite claims from organisers that it would be peaceful. The protesters' demands were met with tear gas.
Some demonstrators were beaten and bundled into police vans, according to reports.
Correspondents say the real goal of the demonstrators is to highlight what they see as the unfair treatment of minority Indians in Malaysia.
Estimates put the crowd at Sunday's rally at more than 5,000.