Thousands of South African students have marched to the capital Pretoria, where President Jacob Zuma is meeting student leaders over tuition fees.
University officials are also at the talks at the Union Buildings, which is the seat of government, amid protests over proposed fee increases.
Police have fired stun grenades and used water canon to stop students outside breaking into the building.
The demonstrations have closed some of the country's top universities.
Students from across the country crammed onto buses and trains to travel to Pretoria to join the march.
President Zuma is expected to address those outside after he finishes meeting with official student and university representatives inside the Union Buildings, according to State Security Minister David Mahl
In a statement on Friday, Mr Zuma acknowledged the "financial difficulties faced by students from poor households", while reiterating that "university fees are determined by universities independently of government".
Universities say they need to increase fees to maintain standards, and have been hit by a fall by in government subsidies.
On Thursday, 29 people were charged with public violence amid the biggest student protests to hit the country since apartheid ended in 1994. They have been released from custody, and the case postponed to February.
The demonstrations began last week at Johannesburg's prestigious University of the Witwatersrand, and have since spread to at least 10 universities, forcing the closure of many of them.
The mainly black students say they cannot afford fee increases and have rejected a government offer to cap increases at 6%, down from the 10% to 12% proposed by the management of universities.
Correspondents say the protests show growing disillusionment with the governing African National Congress (ANC), which took power after minority rule ended in 1994, over high levels of poverty, unemployment and corruption in government.
Many black students say they come from poor families, and fee increases will rob them of the opportunity to continue studying.
Financially better-off white students have joined the protest, mainly to show solidarity with the black students.