Workers stayed home, shops were shut and buses sat idle across South Africa on Tuesday, as fears mounted that planned anti-immigrant marches would descend into violence.

Many foreigners from African countries avoided coming to work, and thousands had already fled ahead of Tuesday's deadline -- set by the demonstrators -- for all undocumented migrants to leave.

Most have interpreted the deadline as a physical threat. Xenophobic protests in South Africa have in the past led to violence against immigrants and their property, with little distinction made between those who entered legally or not.

POLICE AND MILITARY IN THE STREETS

Landlords in the main city Johannesburg and port city of Durban were evicting foreign tenants for fear of their buildings being vandalised, witnesses said.

"All these people, they were chased out by their landlords," Mabako Majole, a leader of the Congolese community, said next to a crowd of 100 people sleeping on the street in downtown Durban.

"All these people are legal. They have documents."

Police and military were deployed to the streets to try to keep order during the marches in several cities, which are expected to attract many thousands of mostly poor or unemployed South Africans.

"The state has the duty and obligation to ensure that those that are demonstrating do so peacefully," Deputy National Commissioner for Policing Tebello Mosikili told a news conference late on Monday.

The latest anti-immigrant sentiment, and a failure by police so far to protect victims of attacks, have tarnished South Africa's post-Mandela reputation as a human rights defender, and strained its relations with the rest of the continent.

Statements by politicians have also endorsed the marchers' concerns, even while they condemned thuggishness.

"South Africans' ... deep concerns about illegal immigration ... are real and they deserve to be heard," President Cyril Ramaphosa said in a statement on Monday.

"But the right to protest ... does not allow people to threaten or intimidate others, or to engage in acts of vandalism or violence," he added.