The United States has imposed targeted visa restrictions on certain South African nationals over policies that Washington says are linked to racial discrimination, incitement of violence and uncompensated land seizures.

US Secretary of State Marco Rubio said the measures would affect individuals responsible for, or complicit in, implementing policies that allow uncompensated land seizures or racial discrimination.

The restrictions do not constitute a blanket visa ban on South African citizens. The US government has not identified the individuals affected or disclosed the number of people who could be subject to the measures.

The move is expected to further strain relations between Washington and Pretoria, amid longstanding disagreements over land reform, racial inequality and the treatment of minority groups in South Africa.

The South African government has defended its land reform policies, saying they are intended to address the legacy of apartheid and persistent inequalities in land ownership. Pretoria has also rejected allegations that Afrikaners are being persecuted.

The latest restrictions are being imposed under a provision of US immigration law that permits visa sanctions where an individual's entry into the United States could have serious adverse foreign-policy consequences.

The announcement represents another escalation in diplomatic tensions between the United States and South Africa.