U.S. President Barack Obama visited the family of the gravely ill Nelson Mandela Saturday while police clashed with several hundred anti-U.S. protesters on the campus of the nearby University of Johannesburg.

"Today I had the privilege of meeting with members of the Mandela family at the Nelson Mandela Foundation in Johannesburg, South Africa, and spoke by telephone with Mrs. Graca Machel, who remained by her husband's side in the hospital in Pretoria," the president said in a statement during his first visit to South Africa.

“I am humbled by [the Obama family's] comfort and messages of strength and inspiration, which I have already conveyed to Madiba,” said Machel in a written statement, referring to Mandela’s Xhosa tribal name. Machel, a human rights activist in her own right, is Mandela's third wife and the widow of the first president of Mozambique.

Mandela remains in critical condition at the Medi-Clinic Heart Hospital in Pretoria, where thousands of well-wishers and dozens of media trucks have gathered in anticipation that South Africa’s anti-apartheid leader and first black president, who is 94, could die at any moment. Obama said he would not complicate matters by visiting the hospital.

“I don't need a photo op," the president said Friday on his way to South Africa, according to NBC News. "The last thing I want to do is be intrusive.” On Friday, Mandela’s former wife Winnie Madikizela-Mandela said his condition had improved, but he remains in critical condition and at his age has a strong chance of succumbing. On Saturday, however, President Jacob Zuma said Mandela's condition was improving.

Earlier on Saturday the president and first lady Michelle Obama traveled to the University of Johannesburg, about 10 miles away from where the president met privately with Mandela family members, to host a town hall-style meeting with young South Africans, and other young people across Africa via video.

The university’s website said Obama visited student leaders “anticipating engaging with Barack Obama about issues concerning the youth.” The event was televised in several South African countries, including Nigeria and Uganda, according to the Mail & Guardian, a local newspaper.

But outside the event, other youths were less impressed and instead used the president’s visit to voice their dissent over several issues regarding Obama’s foreign policy, including drone strikes in the Muslim world and U.S. support of "apartheid Israel."

The so-called "No, You Can't Honour Obama,” or Nobama, campaign is staging demonstrations in Pretoria, Cape Town and Soweto during Obama’s two-day visit.

Prior to the president’s arrival at the university, police fired rubber bullets and tossed stun grenades to disperse a crowd of “several hundred” student protesters. Police clutching shotguns were seen pushing protestors away.

"I feel my rights are being infringed," 24-year-old Bilaal Qibr, who was at the protest, told a USA Today reporter. "We can't protest anymore. Personally, I feel like this is an extension of the U.S.