Police in India have fired tear gas to disperse hundreds of students rallying against affirmative action plans
The protests in Delhi came a day after the cabinet approved a draft bill to reserve places for lower castes in state-funded professional colleges.
The number of places reserved for Dalits (formerly Untouchables) and tribals is to double to nearly 50%.
Critics of the bill say it will lead to lower educational standards. Millions of lower caste Indians support it.
Protesters in Delhi marched towards the house of Sonia Gandhi, leader of the Congress party which heads the federal government, to express their unhappiness at the government's proposals.
They broke through a police cordon leading to Mrs Gandhi's residence and there were scuffles between protesters and police.
Demonstrators have threatened to strike if the bill is tabled in parliament, which is expected later this week.
In May, doctors and medical students in Delhi and several other cities went on strike in protest at the government move.
The strike was called off three weeks later after the Supreme Court ordered the doctors to return to work.
Currently, 22.5% of seats are reserved for Dalits and tribals in state-funded professional colleges.
The bill seeks to set aside another 27% for Other Backward Classes, taking the total reserved seats to 49.5%.
The plan has the support of millions of lower caste Indians and other disadvantaged groups.
Despite laws banning discrimination, India's lower castes remain at the bottom of society and are poorly represented in major professions.
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